U.S. patent number 7,604,832 [Application Number 10/927,155] was granted by the patent office on 2009-10-20 for film forming method, film forming apparatus, pattern forming method, and manufacturing method of semiconductor apparatus.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Tatsuhiko Ema, Kei Hayasaki, Shinichi Ito, Rempei Nakata, Katsuya Okumura, Nobuhide Yamada.
United States Patent |
7,604,832 |
Ito , et al. |
October 20, 2009 |
Film forming method, film forming apparatus, pattern forming
method, and manufacturing method of semiconductor apparatus
Abstract
There is disclosed a film forming method comprising continuously
discharging a solution adjusted so as to spread over a substrate by
a given amount to the substrate through a discharge port disposed
in a nozzle, moving the nozzle and substrate with respect to each
other, and holding the supplied solution onto the substrate to form
a liquid film, wherein a distance h between the discharge port of
the nozzle and the substrate is set to be not less than 2 mm and to
be in a range less than 5.times.10.sup.-5 q.gamma. (mm) given with
respect to a surface tension .gamma. (N/m) of the solution,
discharge speed q (m/sec) of the solution continuously discharged
through the discharge port, and a constant of 5.times.10.sup.-5
(msec/N).
Inventors: |
Ito; Shinichi (Yokohama,
JP), Ema; Tatsuhiko (Kamakura, JP),
Hayasaki; Kei (Kamakura, JP), Nakata; Rempei
(Kamakura, JP), Yamada; Nobuhide (Tokyo,
JP), Okumura; Katsuya (Tokyo, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Tokyo, JP)
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Family
ID: |
27670278 |
Appl.
No.: |
10/927,155 |
Filed: |
August 27, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050022732 A1 |
Feb 3, 2005 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10352954 |
Jan 29, 2003 |
6800569 |
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Foreign Application Priority Data
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Jan 30, 2002 [JP] |
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2002-022382 |
Feb 8, 2002 [JP] |
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2002-031911 |
Apr 2, 2002 [JP] |
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2002-100516 |
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Current U.S.
Class: |
427/8; 438/758;
427/427.3; 427/425; 427/385.5; 427/350; 427/240; 118/713; 118/712;
118/708; 118/665; 118/52; 118/323; 118/321; 118/320 |
Current CPC
Class: |
H01L
21/6715 (20130101); H01L 21/02164 (20130101); H01L
21/31633 (20130101); H01L 21/02126 (20130101); H01L
21/288 (20130101); H01L 21/02282 (20130101); H01L
21/022 (20130101) |
Current International
Class: |
B05D
1/02 (20060101); B05D 3/12 (20060101) |
Field of
Search: |
;427/240,425,8,427.3,350,385.5 ;118/52,320,665,708,712,713,321,323
;438/758 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1304167 |
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Jul 2001 |
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CN |
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59-92530 |
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May 1984 |
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JP |
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2-220428 |
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Sep 1990 |
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JP |
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2-233174 |
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Sep 1990 |
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JP |
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6-151295 |
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May 1994 |
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JP |
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7-321001 |
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Dec 1995 |
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JP |
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8-222502 |
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Aug 1996 |
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8-316311 |
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Nov 1996 |
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JP |
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9-92134 |
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JP |
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09-276781 |
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JP |
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2842909 |
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Oct 1998 |
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JP |
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11-243043 |
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JP |
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2000-77307 |
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Mar 2000 |
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JP |
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2000-77326 |
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Mar 2000 |
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JP |
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2000-79366 |
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Mar 2000 |
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JP |
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2000-188251 |
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Jul 2000 |
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JP |
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2001-148338 |
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May 2001 |
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JP |
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2001-168021 |
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Jun 2001 |
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JP |
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2001-170546 |
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Jun 2001 |
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JP |
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2001-176765 |
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Jun 2001 |
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JP |
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2001-176781 |
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Jun 2001 |
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JP |
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2001-176786 |
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Jun 2001 |
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JP |
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2001-232250 |
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Aug 2001 |
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JP |
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2001-232269 |
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Aug 2001 |
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JP |
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2001-237179 |
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Aug 2001 |
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JP |
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2001-239198 |
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Sep 2001 |
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JP |
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2001-291660 |
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Oct 2001 |
|
JP |
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2001-310155 |
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Nov 2001 |
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JP |
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Other References
Notification of Reasons for Rejection from the Japanese Patent
Office, dated Oct. 31, 2006, in counterpart Japanese Patent
Application No. 2004-367913. cited by other .
First Notification of Reasons for Rejection, issued by Chinese
Patent Office, dated Feb. 4, 2005, in Chinese Patent Application
No. 03102108.5, and English-language translation thereof. cited by
other .
Shinichi Ito, "Liquid Film Forming Method and Solid Film Forming
Method", U.S. Appl. No. 10/202,657, filed Jul. 25, 2002. cited by
other .
Nobuhide Yamada et al., "Method of Forming Coating Film, Method of
Manufacturing Semiconductor Device and Coating Solution", U.S.
Appl. No. 10/112,951, filed Apr. 2, 2002. cited by other .
Shinichi Ito et al., "Film Formation Method, Semiconductor Element
and Method Thereof, and Method of Manufacturing a Disk-Shaped
Storage Medium", U.S. Appl. No. 09/842,403, filed Apr. 26, 2001.
cited by other .
Tatsuhiko Ema et al., "Film Forming Method, Film-Forming Apparatus
and Liquid Film Drying Apparatus", U.S. Appl. No. 09/961,288, filed
Sep. 25, 2001. cited by other .
Notification of Reasons for Rejection issued by the Japanese Patent
Office, mailed Oct. 19, 2004, in Japanese Patent Application No.
2002-022382, and English-language translation thereof. cited by
other .
Notification of Reasons for Rejection issued by the Japanese Patent
Office, mailed Oct. 19, 2004, in Japanese Patent Application No.
2002-031911, and English-language translation thereof. cited by
other .
Office Action mailed Dec. 12, 2008, from the State Intellectual
Property Office of the People's Republic of China in counterpart
Chinese Patent Application No. 2006100720417, and English language
translation thereof. cited by other.
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Primary Examiner: Jolley; Kirsten C
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a divisional of application No. 10/352,954, filed Jan. 29,
2003, now U.S. Pat. No. 6,800,569 which claims priority from prior
Japanese Patent Applications No. 2002-22382, filed Jan. 30, 2002;
No. 2002-31911, filed Feb. 8, 2002; and No. 2002-100516, filed Apr,
2, 2002. The entire contents of these applications are incorporated
herein by reference.
Claims
What is claimed is:
1. A film forming method comprising: combining a linear movement in
a column direction in which a nozzle passes along a substrate from
one end of the substrate to the other end of the substrate with a
movement in a row direction inside or outside the substrate to move
the nozzle and substrate with respect to each other; continuously
discharging a solution adjusted so as to spread over the substrate
by a given amount through a discharge port disposed in the nozzle;
holding the discharged solution on the substrate; and forming a
liquid film, further comprising: obtaining a deviation amount of a
discharge amount of the solution from a desired value with respect
to a discharge position of the solution, when the solution is
discharged onto the substrate from the nozzle moving in a first
column; and controlling the discharge amount in an arbitrary
position in a second column so as to compensate for the deviation
amount obtained in an adjacent discharge position in the first
column, when the solution is discharged onto the substrate from the
nozzle moving in a second column disposed adjacent to the first
column.
2. The film forming method according to claim 1, wherein the
controlling of the discharge amount of the solution supplied onto
the substrate from the nozzle moving in the second column
comprises: controlling at least one of a movement speed of the
nozzle and a discharge speed of the solution from the nozzle.
3. The film forming method according to claim 2, further
comprising: leveling the surface of the liquid film by fluidity of
the solution; and removing a solvent in the liquid film to form a
solid film including the solvent.
4. The film forming method according to claim 3, wherein the
removing of the solvent in the liquid film comprises: rotating the
substrate.
5. The film forming method according to claim 3, wherein the
removing of the solvent in the liquid film comprises: exposing the
substrate under a reduced pressure; or heating the liquid film.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a film forming method comprising:
moving a substrate and nozzle with respect to each other; dropping
solution onto the substrate from a solution discharge nozzle; and
forming a liquid film of the solution on the substrate.
2. Description of the Related Art
To use a spin coating method in a lithography process and
interlayer film formation, most of the solution dropped onto a
substrate is discharged off the substrate, and a film is formed
with the remaining several percent of the solution. Therefore,
there is much waste, and the environment is adversely affected.
Moreover, there has been a problem that turbulence is generated in
an outer peripheral portion of a square substrate or a circular
substrate having a large diameter of 12 inches or more, making the
film thickness nonuniform in that portion.
As a method of uniformly coating the whole surface of the substrate
without wasting in Jpn. Pat. Appln. KOKAI Publication No. 2-220428,
a method is described which comprises: dropping resist from a large
number of nozzles arranged in one row; and spraying a gas or
solution onto a film forming surface from behind the nozzles to
obtain a uniform film. Further, in Jpn. Pat. Appln. KOKAI
Publication No. 6-151295, a large number of spray ports are
disposed in a bar; and the resist is dropped onto the substrate
from the ports to obtain a uniform film. Furthermore, in Jpn. Pat.
Appln. KOKAI Publication No. 7-321001, a method is described
comprising: using a spray head in which a large number of jet holes
are formed to spray the resist; and moving the head with respect to
the substrate to coat the substrate. In all of these coating
apparatuses, a plurality of dropping or spray nozzles are
transversely arranged in a row, so as to scan the nozzles along the
substrate surface and a the uniform film. In addition to these
coating methods, there is a method using one solution discharge
nozzle, and scanning the nozzle to form a liquid film. This method
has a problem that the treatment time per substrate depends on the
operation method of the nozzles, and the amount of solution used
becomes enormous.
As an apparatus for solving the problem, in Jpn. Pat. Appln. KOKAI
Publication No. 9-92134, a method is disclosed which comprises:
reciprocating/moving the solution discharge nozzle over the
substrate to drop the solution onto the substrate. The method
further comprises: stopping liquid supply in each terminal end of
the reciprocating/moving on the substrate; and re-supplying the
solution in a start point to form the coating film. However, the
solution amount supplied onto the substrate slightly differs due to
uneven liquid supply caused by stoppage and restart of liquid
supply at the terminal end and start point, and a problem has
occurred that film thickness uniformities of the liquid film and
solid film formed from the liquid film are deteriorated.
On the other hand, in Jpn. Pat. Appln. KOKAI Publication Nos.
2000-77307, 2000-77326, 2000-79366, 2000-188251, 2001-148338,
2001-168021, 2001-170546, 2001-176781, 2001-176786, 2001-232250,
and 2001-232269, a method is disclosed comprising: maintaining the
discharge of the solution even in a turn-back portion in the
reciprocating movement of the solution discharge nozzle; and
supplying a coating film in which a film thickness distribution at
an edge vicinity (the vicinity of turn-back of reciprocating
movement) is not deteriorated. However, in the coating apparatus
described in these publications, a distance between the solution
discharge nozzle and substrate is not considered. Depending on the
discharge speed from the solution discharge nozzle, surface tension
of the solution, and distance between the solution discharge nozzle
and substrate, in a process of spread of liquid flow before the
solution reaches the substrate, liquid drops are produced by the
surface tension of the liquid, and the liquid drops which have
reached the substrate are sputtered, causing a problem of mist or
vapor.
Moreover, in the above-described forming method in the liquid film,
in each region of the substrate surface to be treated, because of
differences of physical properties, discharge pressure of the
nozzle, further variations in discharge amount of the solution, or
turbulence of air currents at the coating time, the film thickness
of the liquid film does not become uniform, and sometimes varies
over the whole surface of the substrate. When a solvent in the
liquid film is vaporized in this state, a film of a solid content
(=solid film) is formed on the substrate with low flatness in
accordance with the film thickness distribution of the liquid
film.
Moreover, even when the liquid film is formed in a excellent
flatness state, when a drying process is thereafter executed so as
to vaporize the solvent, aggregation occurs toward the middle
portion of the substrate. In this manner, the solid content moves
with the movement of the liquid film in a transverse direction, and
a difference in film thickness is generated in the movement
direction.
When a such photo resist film which is formed using the such method
is subjected to exposure and development processes to form a
pattern, a critical dimension (CD) error is generated in the
pattern. In a process in which this pattern is used as a mask to
subject a lower layer film (e.g.: insulating film, and conductive
wiring film) to etching processing, the CD error is further
enlarged. This was an effect of reaucing the yield.
As disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-237179,
with respect to the variation in thickness of the liquid film,
there has heretofore been a method comprising: forming the liquid
film; subsequently exposing the film to a solvent vapor to promote
fluidity of the solution; and performing a so-called leveling
treatment so that the surface of the liquid film is flatted by the
surface tension.
However, in the prior-art leveling treatment, the solvent is
unnecessarily supplied to the surface of the liquid film, and the
film thickness is uneven. Inclination is generated in the film
thickness of the liquid film (e.g., peripheral edge) by an
inadequate condition.
Additionally, a manufacturing process of the semiconductor
apparatus comprises: coating the substrate surface with a resist
solution in which resist materials such as a resin, dissolution
inhibitor (dissolution inhibitor group), and acid generating
material (acid generation group) are dissolved in organic solvent
(ethyl lactate, etc.) to form the liquid film; and subsequently
evaporating the solvent in the liquid film to form the resist film.
The resist film formed on the substrate is exposed to light, then
bake-treated, cooled, and developed to form a resist pattern.
Some of the resist patterns formed as described above have a
problem that the upper part of the resist pattern is rounded. Since
the upper surface of the resist film is exposed to a developing
liquid for a long time, the upper part becomes rounded. To solve
this problem, a layer containing many dissolution inhibitor can be
formed in the surface layer.
However, to form the layer containing many dissolution inhibitor in
the surface layer, a prior art method has to comprise: coating the
substrate with a first resist solution film; baking and forming a
first resist film; coating the first resist film with a second
resist solution film using a resist solution which containing the
dissolution inhibitor more than the resist solution used in forming
the first resist film; and baking and forming the second resist
film. In this method, two resist films have to be separately
formed, which lengthens manufacturing time.
As a prior-art method of forming the coating film on the substrate,
there is a method comprising: relatively moving a discharge nozzle
which discharges a given amount of solution on the substrate;
discharging the solution over the whole surface of the substrate to
form a liquid film; and thereafter evaporating the solvent by an
appropriate dry method to form the film. In this method, a solution
which has a small solid content and has a low viscosity in a range
of about 0.001 Pas to 0.010 Pas (1 cp to 10 cp) is used. When the
liquid film is formed on a substrate having a stepped portion in
this coating method, the formed liquid film is fluidized by
gravity, and a concave/convex portion is smoothed. A difference is
generated in the thickness of the finally prepared coated film,
that is, the film thickness of the concave portion increases and
that of the convex portion decreases. As a result, there is a
problem that a film having a uniform thickness cannot be formed on
the substrate surface.
BRIEF SUMMARY OF THE INVENTION
(1) According to one aspect of the present invention, there is
provided a film forming method of discharging a solution from a
discharge port of a nozzle onto the substrate, and then providing
relative movement between the nozzle and the substrate while
keeping the liquid discharging on the substrate, so as to form a
liquid film on the substrate,
wherein a distance h between the discharge port of the nozzle and
the substrate is set to be not less than 2 mm and to be less than
Aq.gamma. (mm),
wherein q (m/sec) denotes a discharge speed of the solution
continuously discharged through the discharge port,
.gamma. (N/m) denotes a surface tension of the solution, and
A (msec/N) is 5.times.10.sup.-5.
(2) According to another aspect of the present invention, there is
provided a film forming method comprising:
registering a surface tension .gamma. (N/m) of a solution adjusted
so as to spread over the substrate by a given amount;
calculating a distance h between a discharge port of a nozzle and a
substrate, which is not less than 2 mm and is less than
5.times.10.sup.-5 q.gamma. (mm), from a discharge speed q (m/sec)
of the solution continuously discharged to the substrate through
the discharge port of the nozzle, surface tension .gamma. (N/m) of
the solution, and constant of 5.times.10.sup.-5 (msec/N); and
discharging a solution from a discharge port of a nozzle onto the
substrate, and then providing relative movement between the nozzle
and the substrate while keeping the liquid discharging on the
substrate.
(3) According to further aspect of the present invention, there is
provided a film forming method comprising: combining a linear
movement in a column direction in which a nozzle passes along a
substrate from one end of the substrate to the other end of the
substrate with a movement in a row direction inside or outside the
substrate to move the nozzle and substrate with respect to each
other; continuously discharging a solution adjusted so as to spread
over the substrate by a given amount through a discharge port
disposed in the nozzle; holding the discharged solution on the
substrate; and forming a liquid film, further comprising:
obtaining a deviation amount of a discharge amount of the solution
from a desired value with respect to a discharge position of the
solution, when the solution is discharged onto the substrate from
the nozzle moving in a first column; and
controlling the discharge amount in an arbitrary position in a
second column so as to compensate for the deviation amount obtained
in an adjacent discharge position on the first column, when the
solution is discharged onto the substrate from the nozzle moving on
a second column disposed adjacent to the first column.
(4) According to still another aspect of the present invention,
there is provided a film forming method comprising: moving a nozzle
in a diameter direction of a substrate over the substrate which
rotates; continuously discharging a solution adjusted so as to
spread over the substrate by a given amount through a discharge
port disposed in the nozzle; and holding the supplied solution on
the substrate to form a liquid film, further comprising:
obtaining a deviation amount of a supply amount of the solution
from a desired value with respect to a discharge position of the
solution, when the solution is supplied onto the substrate from the
nozzle; and
controlling the supply amount of the solution discharged to a first
position, so as to compensate for the deviation amount in a second
position which is disposed adjacent to the first discharge position
in the diameter direction of the substrate and to which the
solution has already been discharged, during the supply of the
solution into the first position of the substrate from the
nozzle.
(5) According to further aspect of the present invention, there is
provided a film forming method comprising: combining a linear
movement in a column direction in which a nozzle passes along a
substrate from one end of the substrate to the other end of the
substrate with a movement in a row direction inside or outside the
substrate to move the nozzle and substrate with respect to each
other; continuously discharging a solution adjusted so as to spread
over the substrate by a given amount through a discharge port
disposed in the nozzle; holding the discharged solution on the
substrate; and forming a liquid film, further comprising:
cutting off the solution discharged onto the substrate from the
nozzle so that a supply start point and supply end point of the
solution discharged onto the substrate from the nozzle reach a
liquid film edge forming position apart from each edge of the
substrate by a given width d during the movement of the nozzle in
the column direction.
(6) According to further aspect of the present invention, there is
provided a film forming method comprising: combining a linear
movement of a column direction in which a nozzle passes along a
circular substrate from one end of the circular substrate through
the other end of the substrate with a movement of a row direction
in the vicinity of an edge of the circular substrate to move the
nozzle and substrate with respect to each other; continuously
discharging a solution adjusted so as to spread over the circular
substrate by a given amount to the substrate through a discharge
port disposed in the nozzle; holding the discharged solution onto
the substrate; and forming a liquid film over the whole surface of
the substrate to an end position from a start position,
wherein a movement speed of the column direction of the nozzle in
the vicinity of the start position is set to be lower than the
movement speed of the column direction of the nozzle in a middle
position of the substrate; and
the movement speed of the column direction of the nozzle in the
vicinity of the end position is set to be higher than the movement
speed of the column direction of the nozzle in the middle position
of the substrate.
(7) According to further aspect of the present invention, there is
provided a film forming method comprising: combining a linear
movement of a column direction in which a nozzle passes along a
circular substrate from one end of the circular substrate through
the other end of the substrate with a movement of a row direction
in the vicinity of an edge of the circular substrate to move the
nozzle and substrate with respect to each other; continuously
discharging a solution adjusted so as to spread over the circular
substrate by a given amount to the substrate through a discharge
port disposed in the nozzle; holding the discharged solution onto
the substrate; and forming a liquid film over the whole surface of
the substrate to an end position from a start position,
wherein a movement distance of the row direction of the nozzle in
the vicinity of the start position is set to be longer than the
movement distance of the row direction of the nozzle in a middle
position of the circular substrate; and
the movement distance of the row direction of the nozzle in the
vicinity of the end position is set to be shorter than the movement
distance of the row direction of the nozzle in the middle position
of the substrate.
(8) According to further aspect of the present invention, there is
provided a film forming method comprising: combining a linear
movement of a column direction in which a nozzle passes along a
circular substrate from one end of the circular substrate through
the other end of the substrate with a movement of a row direction
in the vicinity of an edge of the circular substrate to move the
nozzle and substrate with respect to each other; continuously
discharging a solution adjusted so as to spread over the circular
substrate by a given amount to the substrate through a discharge
port disposed in the nozzle; holding the discharged solution onto
the substrate; and forming a liquid film over the whole surface of
the substrate to an end position from a start position,
wherein a time interval from when the solution supply to the
substrate by the movement of the column direction of the nozzle
including the movement of the row direction of the nozzle is
temporarily discontinued until the solution supply to the substrate
by the movement of the column direction of the nozzle is restarted
is set to be constant.
(9) According to one aspect of the present invention, there is
provided a film forming method comprising:
forming a liquid film constituted of a solution including a first
solvent and solid content on a substrate;
containing the substrate in a container;
starting a leveling treatment to flat the surface of the liquid
film in a state in which an atmosphere including a second solvent
is formed in the container;
measuring flatness of the surface of the liquid film during the
leveling treatment;
controlling at least one of the atmosphere in the container and
temperature of the substrate based on the measured flatness during
the leveling treatment to enhance the flatness of the surface of
the liquid film;
ending the leveling treatment; and
forming a solid film including the solid content on the
substrate.
(10) According to further aspect of the present invention, there is
provided a film forming method comprising:
forming a liquid film including a solid content and solvent on a
substrate;
starting a drying treatment to remove the solvent in the liquid
film;
measuring flatness of the surface of the liquid film during the
drying treatment;
controlling at least one of the atmosphere of environment in which
the substrate exists, temperature of the substrate, and rotation
speed of the substrate based on the measured flatness during the
drying treatment to enhance the flatness; and
ending the drying treatment to form a solid film including the
solid content on the substrate.
(11) According to one aspect of the present invention, there is
provided a film forming apparatus comprising:
a support unit to support a substrate on the surface of which a
liquid film including a first solvent is formed;
a container including the support unit disposed in an inner
space;
a gas supply unit which includes a discharge port and which
supplies gas including a second solvent into the container through
the discharge port;
an exhaust unit which exhausts air from the atmosphere in the
container;
an optical system which irradiates the liquid film on the substrate
supported on the support unit with light, receives reflected light
from the liquid film, and obtains reflected light intensity;
and
an analysis unit which analyzes the reflected light intensity
obtained by the optical system to measure flatness of the liquid
film surface and which controls the exhaust unit and gas supply
unit so as to enhance the measured flatness.
(12) According to another aspect of the present invention, there is
provided a film forming method comprising:
forming a liquid film including a solution in which a first
material is dissolved in a solvent on a substrate;
removing the solvent from the liquid film, until a substrate side
of the liquid film solidifies and the solvent remains on a side
opposite to the substrate side;
supplying a second material into the liquid film in a state in
which the solvent remains in a surface layer of the liquid film;
and
removing the solvent remaining in the liquid film to form a solid
film.
(13) According to further aspect of the present invention, there is
provided a film forming method comprising:
preparing a substrate which includes a concave/convex portion
having a stepped portion height of d and in which a rate of an area
of the convex portion to the whole area is a (1>a>0) and a
rate of an area of the concave portion to the whole area is
1-a;
discharging a solution in which a solid content is dissolved in a
solvent, moving a discharge nozzle and substrate with respect to
each other, and forming a liquid film on the substrate; and
removing the solvent in the liquid film, and forming a solid film
including the solid content,
wherein the liquid film is formed so that a thickness h of the
liquid film satisfies a relation of h>(11-a)d.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a diagram showing a schematic constitution of a liquid
film forming apparatus according to a first embodiment;
FIGS. 2A to 2D are sectional views showing a film forming process
according to the first embodiment;
FIG. 3 is a diagram showing concept of an observation system for
use in obtaining a distance between a discharge port of a solution
discharge nozzle and a substrate;
FIG. 4 is a diagram showing a relation of a discharge speed of the
solution with a distance H.sub.p from the discharge port in a
liquid drop state;
FIG. 5 is an explanatory view showing definition of a region D in
which spread of the solution discharged through the discharge port
is stabilized;
FIG. 6 is an enlarged view of a section of the discharge port of
the solution discharge nozzle;
FIG. 7 is a diagram showing a relation of a film thickness
distribution in a wafer surface to a distance h between the
discharge nozzle of the solution discharge nozzle and the
substrate;
FIG. 8 is a diagram showing a relation of the number of particles
per wafer with respect to distance h between the discharge port and
substrate;
FIG. 9 is an explanatory view of a method of calculating a
discharge speed q of the solution;
FIG. 10 is a diagram showing a liquid film thickness (supply
amount) with respect to a discharge position, when a liquid film is
formed by a PID control;
FIG. 11 is a diagram showing a liquid film thickness (supply
amount) with respect to the discharge position, when the liquid
film is formed by a control method according to a second
embodiment;
FIG. 12 is a diagram showing a film with respect to the discharge
position of a solid film obtained by removing a solvent in the
liquid film formed by the control method according to the related
art and present embodiment;
FIGS. 13A, 13B are diagrams showing a schematic constitution of a
liquid film forming apparatus according to a third embodiment;
FIG. 14 is a diagram showing an installation relation of a shutter
position with respect to a track of the solution discharge
nozzle;
FIGS. 15A, 15B are diagrams showing an error of a coat region
generated in a shutter;
FIG. 16 is a diagram showing an edge profile of the liquid film
formed by a related-art shutter position;
FIG. 17 is a diagram showing the edge profile of the liquid film
formed by the shutter position according to the present
embodiment;
FIGS. 18A, 18B are explanatory views of a force applied to the
liquid film edge at a substrate rotation time;
FIGS. 19A, 19B are diagrams showing the schematic constitution of
the liquid film forming apparatus according to the third
embodiment;
FIGS. 20A, 20B are diagrams schematically showing a spread state of
a liquid line applied in a first column at a coating time of a
second column, and boundary of a unit liquid film in the finally
obtained liquid film in a coating start/end portion at a time of
preparation of the liquid film using the coating apparatus of FIG.
1 according to a fourth embodiment;
FIGS. 21A, 21B are diagrams schematically showing the spread state
of the liquid line applied in the first column at the coating time
of the second column, and boundary of the unit coat film in the
finally obtained liquid film in the vicinity of a substrate center
at the preparation time of the liquid film using the coating
apparatus of FIG. 1 according to the fourth embodiment;
FIG. 22 is a diagram showing a relative thickness of a row
direction of the film formed according to the related art and
fourth embodiment;
FIG. 23 is a schematic diagram showing an apparatus for treating
the liquid film on the substrate according to a fifth
embodiment;
FIG. 24 is a plan view showing a schematic constitution of a
temperature control plate according to the fifth embodiment;
FIG. 25 is a diagram relating to a treatment method of the liquid
film on the substrate in the fifth embodiment;
FIG. 26A is a diagram showing a change of the film thickness of the
liquid film in each position on the substrate with time in a
leveling treatment according to the fifth embodiment;
FIG. 26B is a diagram showing a change of solvent concentration in
gas supplied into a chamber with time in the leveling treatment
according to the fifth embodiment;
FIG. 26C is a diagram showing a change of temperature of middle and
peripheral edge plates in the leveling treatment according to the
fifth embodiment;
FIG. 27A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 27B is a diagram showing the change of pressure in the chamber
with time in the leveling and drying treatments according to the
fifth embodiment;
FIG. 27C is a diagram showing the change of temperature of middle
and peripheral edge plates in the leveling and drying treatments
according to the fifth embodiment;
FIG. 28A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 28B is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
related-art leveling and drying treatments;
FIG. 28C is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
related-art leveling and drying treatments;
FIGS. 29A, 29B are diagrams showing effects of the fifth
embodiment;
FIG. 30 is a schematic diagram showing an apparatus for treating
the liquid film on the substrate according to a change example of
the fifth embodiment;
FIG. 31A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling treatment according to the fifth embodiment;
FIG. 31B is a diagram showing the change of solvent concentration
in gas supplied into the chamber with time in the leveling
treatment according to the fifth embodiment;
FIG. 31C is a diagram showing the change of temperature of the
middle and peripheral edge plates in the leveling treatment
according to the fifth embodiment;
FIG. 32 is a schematic diagram showing the apparatus for treating
the liquid film on the substrate according to a modification
example of the fifth embodiment;
FIG. 33A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 33B is a diagram showing a change of a flow rate of N.sub.2
gas supplied into the chamber with time in the leveling and drying
treatments according to the fifth embodiment;
FIG. 33C is a diagram showing the change of temperature of the
middle and peripheral edge plates in the leveling and drying
treatments according to the fifth embodiment;
FIG. 34A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 34B is a diagram showing the change of the flow rate of
N.sub.2 gas supplied into the chamber with time in the leveling and
drying treatments according to the fifth embodiment;
FIG. 34C is a diagram showing the change of temperature of the
middle and peripheral edge plates in the leveling and drying
treatments according to the fifth embodiment;
FIG. 35 is a schematic diagram showing the apparatus for treating
the liquid film on the substrate according to a modification
example of the fifth embodiment;
FIG. 36 is a schematic diagram showing the apparatus for treating
the liquid film on the substrate according to the modification
example of the fifth embodiment;
FIG. 37A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 37B is a diagram showing the change of the pressure in the
chamber with time in the leveling and drying treatments according
to the fifth embodiment;
FIG. 37C is a diagram showing a change of rotation speed of the
substrate in the leveling and drying treatments according to the
fifth embodiment;
FIG. 38A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 38B is a diagram showing the change of the flow rate of
N.sub.2 gas supplied into the chamber with time in the leveling and
drying treatments according to the fifth embodiment;
FIG. 38C is a diagram showing the change of rotation speed of the
substrate in the leveling and drying treatments according to the
fifth embodiment;
FIG. 39A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 39B is a diagram showing the change of the flow rate of
N.sub.2 gas supplied into the chamber with time in the leveling and
drying treatments according to the fifth embodiment;
FIG. 39C is a diagram showing the change of rotation speed of the
substrate in the leveling and drying treatments according to the
fifth embodiment;
FIG. 40A is a diagram showing the change of the film thickness of
the liquid film in each position on the substrate with time in the
leveling and drying treatments according to the fifth
embodiment;
FIG. 40B is a diagram showing the change of rotation speed of the
substrate in the leveling and drying treatments according to the
fifth embodiment;
FIGS. 41A to 41E are process sectional views showing a
manufacturing process of a semiconductor apparatus according to a
sixth embodiment;
FIG. 42 is a diagram showing a schematic constitution of the liquid
film forming apparatus according to the sixth embodiment;
FIG. 43 is a diagram showing a forming process of the liquid film
using the liquid film forming apparatus shown in FIG. 42;
FIG. 44 is a diagram showing a shape of a resist pattern prepared
from a resist film formed in a related-art method;
FIG. 45 is a sectional view showing the shape of the resist pattern
prepared using the resist film having a profile which has a higher
dissolution inhibitor material concentration closer to the
surface;
FIGS. 46A to 46C are a process sectional view showing the
manufacturing process of the semiconductor apparatus according to a
seventh embodiment;
FIG. 47 is a diagram showing a distribution of film thickness
direction of oxygen and carbon with respect to Si in an interlayer
insulating film;
FIGS. 48A to 48E are a process sectional view showing the
manufacturing process of the semiconductor apparatus according to
an eighth embodiment;
FIGS. 49A to 49C are a process sectional view showing the
manufacturing process of the semiconductor apparatus according to a
ninth embodiment;
FIG. 50 is a diagram showing a schematic constitution of a pressure
reduction drying treatment unit according to the ninth
embodiment;
FIGS. 51A to 51C are a sectional view showing the film thickness
distribution of the resist film formed on the substrate which has a
stepped portion;
FIG. 52 is a graph showing a ratio of a film thickness difference
with respect to an average film thickness;
FIG. 53 is a sectional view showing the film thickness distribution
of the resist film formed on the substrate according to the ninth
embodiment;
FIG. 54 is a characteristic diagram showing dependence of fluidity
in an edge portion on the liquid film thickness; and
FIG. 55 is a characteristic diagram showing dependence of film
thickness uniformity of a convex portion in the whole substrate
surface on the liquid film thickness.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described hereinafter
with reference to the drawings.
First Embodiment
FIG. 1 is a diagram showing a schematic constitution of a liquid
film forming apparatus according to a first embodiment. FIGS. 2A to
2D are sectional views showing a film forming process according to
the first embodiment of the present invention.
As shown in FIG. 1, a substrate 11 is horizontally laid on a
substrate movement mechanism (not shown). A solution discharge
nozzle 12 is disposed above the substrate 11. The solution
discharge nozzle 12 reciprocates/moves in a direction crossing at
right angles to a movement direction of the substrate 11 by a
nozzle movement mechanism (not shown). The solution discharge
nozzle 12 includes a discharge port through which a solution 14
supplied from a solution supply pump 13 is discharged with respect
to the substrate 11.
A method of forming a liquid film on the substrate 11 comprises:
discharging the solution 14 onto the substrate 11 through a
discharge port of the solution discharge nozzle 12;
reciprocating/moving the solution discharge nozzle 12 in a column
direction; and linearly discharging the solution onto the substrate
11. Moreover, when the solution discharge nozzle 12 is positioned
in a region other than a region on the substrate 11 or outside a
desired film forming region in the substrate, the substrate 11 is
moved in a row direction crossing at right angles to the column
direction of the solution discharge nozzle 12. Note that numeral
number 15 in FIG. 1 denotes the track of the discharged port on the
substrate.
The solution linearly supplied onto the substrate spreads by
fluidity of the solution itself, and linear solutions disposed
adjacent to one another join up, forming liquid film 16.
When the nozzle moves in the row direction as one direction to a
liquid film forming end position from a liquid film forming start
position, the supply of the solution is performed with respect to
substantially the whole substrate 11, and the liquid film 16 is
formed substantially over the whole surface of the substrate 11
(FIG. 2A).
According to circumstances, the unit of FIG. 1 or apparatus (not
shown) is used to perform a leveling treatment by leaving the film
to stand in an atmosphere containing a solvent, and the surface of
the liquid film 16 is flatted (FIG. 2B). That is, when the solution
discharges, the discharge amount fluctuates, and a concave/convex
portion is formed in the surface of a liquid film 16. Then, if
necessary, first the leveling treatment is performed to flat the
surface of the liquid film 16.
The substrate 11 is conveyed into a drying apparatus (not shown).
The solvent in the liquid film 16 is removed by a pressure
reduction or heating mechanism in the drying apparatus (FIG. 2C). A
solid film 17 having a predetermined thickness is formed on the
substrate 11 (FIG. 2D).
In the present embodiment, a procedure will be described
comprising: optimizing a distance between the discharge port of the
solution discharge nozzle 12 and the substrate and produced
position of liquid drops; and supplying the solution onto the
substrate from the solution discharge nozzle in this state, so that
a satisfactory film thickness distribution having few defects is
provided.
FIG. 3 is a diagram showing the concept of an observation system
for use in obtaining the distance between the discharge port of the
solution discharge nozzle and the substrate.
As shown in FIG. 3, a laser light source 21 and video camera for
observation 22 are disposed so as to hold the solution 14
discharged through the discharge port of the solution discharge
nozzle 12. It can easily be judged whether the solution 14
discharged through the discharge port has a liquid drop state by
judging whether or not the laser beam emitted to the solution 14 is
scattered. A region in which scattering is confirmed is regarded as
a liquid drop forming region.
This observation optical system was used to conduct an experiment
in which a relation of a discharge speed with a distance Hp from
the discharge port in the liquid drop state was obtained with
respect to a resist solution including ethyl lactate in the solvent
and including a solid content of 2%. Note that the surface tension
of the resist solution is 30.times.10.sup.-3 N/m and this is
substantially the same as that of the solvent.
FIG. 4 shows the relation of the discharge speed with the distance
Hp from the discharge port through which the solution is in the
liquid drop state. As shown in FIG. 4, it has been found that the
discharge speed has a proportional relation with the distance Hp
for the resist solution used in the experiment. FIG. 4 also shows a
result of similar measurement performed with respect to pure water.
With water, the proportional relation is obtained between the
discharge speed and distance Hp. In addition to these solutions, an
experiment was also carried out with respect to various solutions
of solvents having different surface tensions, such as methanol
(surface tension=22.6.times.10.sup.-3 N/m) and hexane (surface
tension=18.4.times.10.sup.-3 N/m). In all experiments, a
proportional relation was obtained. From these proportional
relations, a relation of a discharge speed q (m/sec) from the
solution discharge nozzle with the distance Hp (mm) is further
represented by the following equation (2) using a surface tension
.gamma. (N/m) of the solution. Hp.gtoreq.5.times.10.sup.-5 q.gamma.
(1) wherein a dimension of a constant 5.times.10.sup.-5 is
msec/N.
It is seen from the equation (1) that the distance h between the
discharge port of the solution discharge nozzle and the substrate
is as follows in supplying the solution having the surface tension
.gamma. (N/m) onto the substrate at the discharge speed q (m/sec):
h<5.times.10.sup.-5 q.gamma..ltoreq.Hp (2)
In the present example, in order to obtain a liquid film having an
average thickness of 15 .mu.m, a constant movement speed of the
solution discharge nozzle on the substrate was set to 1 m/sec, a
pitch of liquid lines on the substrate was set to 0.4 mm, and the
resist solution (surface tension=30.times.10.sup.-3 N/m) including
the solid content of 2% was discharged through the discharge port
having a diameter of 40 .mu.m at a discharge speed of 4.77 m/s. In
this case, from the equation (2), an upper limit h.sub.max of the
distance h was determined as follows: hmax<0.05
[ms/N].times.4.77 [m/s].times.30.times.10.sup.-3 [N/m]=7.16 [mm]
(3)
A lower limit of the distance between the discharge port of the
solution discharge nozzle and the substrate was determined as a
distance to obtain a region D in which the spread of the solution
discharged through the discharge port is substantially stabilized.
FIG. 5 shows a defined region of the stabilized region D. The
solution 41 discharged through a discharge port 21 of the solution
discharge nozzle 12 rapidly spreads immediately after the
discharge, thereafter slowly spreads, and reaches the substrate 11.
The spread differs according to diameter, shape (taper angle), and
length of the discharge port 21 shown in FIG. 6, and viscosity of
the solution. In the above-described coating method, a diluted
solution is obtained at about several times 10.sup.-3 Pas.
Moreover, the discharge port 21 of the solution discharge nozzle 12
having a shape of (length of discharge port)/(diameter of discharge
port) .gtoreq.2 and a taper angle of 70.degree. to 110.degree. was
used. Moreover, the discharge port 21 having a diameter of about 20
to 100 .mu.m was used.
Note that the stabilized region D is defined as a region where a
spread width of 0.8 D.sub.W or more is obtained with respect to a
spread width D.sub.W of the solution discharged in
h=5.times.10.sup.-5 q.gamma.. The viscosity of the solution was set
to a range of 1 to 8.times.10.sup.-3 Pas, the discharge port shape
of the solution discharge nozzle (length of discharge
port)/(diameter of discharge port) was set to a range of 2 to 5,
and the taper angle .theta. of the discharge port was set to a
range of 70.degree. to 110.degree.. In these ranges, a plurality of
nozzles were manufactured on trial in which the diameter of the
discharge port was changed in a range of 20 to 100 .mu.m. The
observation system shown in FIG. 3 was used to change the discharge
speed and measure the distance to the region D from the discharge
port. It has been found that the liquid spread is influenced
particularly by the discharge speed and the taper angle of the
discharge port, but the stabilized region D is obtained in any
condition when the distance from the discharge port was between 1
and 2 mm. It was confirmed that the stabilized region D was reached
at h=1 mm, but with the discharge in this state, the solution
reaching the substrate bounces back and dirties the surface of the
nozzle disposed opposite the substrate. The distance h was changed
to confirm the degree of contamination, and it has been found that
the problem can be solved by making the distance h of 2 mm or more.
From these studies, the lower limit of the distance between the
solution discharge nozzle and substrate may be set to 2 mm. Note
that with the supply of the solution onto the substrate at a
distance of 2 mm or less, the spread of the solution on the
substrate by the fluidity cannot sufficiently be obtained, or the
nozzle is contaminated. Therefore, uniformity of the liquid film
thickness was .+-.10% or more, and only a liquid film inappropriate
for practical use can be obtained.
It is apparent from the above-described studies that the distance h
between the discharge port of the solution discharge nozzle and the
substrate is preferably set as follows: 2
[mm].ltoreq.h<5.times.10.sup.-5 q.gamma. (4)
The apparatus of FIG. 1 was used to adjust the distance h in a
range of 0.5 mm to 10 mm, an 8-inch wafer was coated with the
resist solution to form the liquid film, and further the solvent in
the solution was dried/removed to form a solid film. Here, the
solvent was removed, after the substrate with the liquid film
formed thereon was exposed to an atmosphere of ethyl lactate as
that of the solvent included in the liquid film and the liquid film
was leveled. The substrate on which the liquid film was leveled was
moved into a pressure reduction chamber, the pressure inside the
pressure reduction chamber was reduced, and the solvent was removed
in the state of the pressure held in the vicinity of a saturated
vapor pressure of ethyl lactate. Furthermore, after the pressure
was returned to normal, the substrate was conveyed out of the
pressure reduction chamber, heated at 140.degree. C. on a hot
plate, and any remaining solvent present in the film was removed.
Note that the substrate may directly be heated by a baker, instead
of using a hot plate in times of the solvent in the solution was
dried/removed exposing the substrate to reduced pressure. Moreover,
the substrate may be rotated, and dried by air.
The discharge speed from the discharge port of the solution
discharge nozzle was set to 4.77 m/sec and doubled to 9.54 m/sec,
and the liquid film was formed. Note that the movement speed of the
solution nozzle was set to 1 m/sec with the discharge speed of 4.77
m/sec and the movement speed of the solution discharge nozzle was
set to 2 m/sec with the discharge speed of 0.54 m/sec so as to
obtain the same liquid film thickness at both the discharge speeds.
Moreover, when the discharge speed was 4.77 m/s, an upper-limit
distance Hp was 7.16 mm. When the discharge speed was 9.54 m/s, the
upper-limit distance Hp was 14.3 mm.
With respect to the formed solid film, a relation of a film
thickness distribution (range %) in a wafer surface to the distance
h between the discharge nozzle of the solution discharge nozzle and
the substrate is shown in FIG. 7. Moreover, a relation of the
number of particles per wafer with respect to the discharge
port-substrate distance h is shown in FIG. 8.
As seen from FIG. 7, with the resist solution, for the film
thickness uniformity, when the discharge port-substrate distance h
was set to 3 mm or more, it was possible to obtain a stabilized
value. Note that to form interlayer films or to apply a solution
including a low-dielectric material, a range of film thickness
uniformity of about 5% is sufficient, and therefore the distance is
preferably 2 mm or more.
For the result of particles of FIG. 8, a satisfactory result was
obtained in a range which satisfied the equation (4) with respect
to each discharge speed, and the result was also obtained that the
number of defects increased in another region. The reason why there
are many defects with h.ltoreq.2 mm is that the distance between
the nozzle and substrate is short, therefore the solution sputtered
on the substrate stuck to the nozzle, and this discharged onto the
substrate, generating defects, or that the solution contacting the
nozzle was scattered as a mist, and stuck to the substrate,
generating defects. One reason why the particles increase at an
upper-limit distance Hp or more distance is thought to be that a
part of the solution discharged as described above forms micro
liquid drops, providing a mist which generates the particles. Due
to this, the distance h between the discharge port of the solution
discharge nozzle and the substrate may be set in the range which
satisfies the condition of the equation (4).
It is possible to automatically set the distance h between the
discharge port of the solution discharge nozzle and the substrate
in the coating apparatus. In this case, the coating apparatus is
constituted so that the surface tension .gamma. (N/m) of the
solution to be applied can be registered. On an apparatus side, an
appropriate distance h may be calculated by the equation (4) in
accordance with the registered surface tension .gamma. and
discharge speed q (m/sec) at this time. The distance between the
discharge port of the solution discharge nozzle and the substrate
is adjusted so as to reach the obtained appropriate distance h
before the solution is supplied to the substrate. For the
adjustment of the distance, the substrate may be moved
upwards/downwards, a solution discharge nozzle driving system may
be moved, or both may be moved.
The discharge speed q (m/sec) may directly be inputted by an
operator, or is preferably automatically calculated in the coating
apparatus. FIG. 9 is an explanatory view of a method of calculating
the discharge speed q of the solution, when relative movement of
the solution discharge nozzle and substrate is constituted of a
combination of linear movement of the column direction of the
solution discharge nozzle passing along the substrate from one end
of the substrate through to the other end of the substrate with
movement of the row direction outside the substrate. As shown in
FIG. 9, assuming that for a discharge speed q (m/sec) of a solution
82, a desired average liquid film thickness of a liquid film 83 is
df, a movement pitch of the row direction of the nozzle is p
(=width of unit liquid film), a radius of a discharge hole 81 of
the solution discharge nozzle is r, and the speed of the linear
movement of the column direction of the solution discharge nozzle
passing along the substrate from one end of the substrate to the
other end of the substrate is v (m/s), the following relation is
established from a relation in which a liquid amount of a coat
region is equal to an amount of discharged liquid:
d.sub.f[m].times.p[m].times.v[m/s]=.pi.(r[m]).sup.2q[m/s] (5) When
this relation is organized with respect to the discharge speed q of
the solution 82, the following relation is obtained:
q=d.sub.f.times.p.times.v/.pi.r.sup.2 (6) Note that the average
liquid film thickness can easily be obtained using a desired
average film thickness of the solid film, solid content
concentration in the solution, and density of solid and liquid
films by means described in a conventional chemistry textbook.
For the relative movement of the solution discharge nozzle and
substrate, even when the solution discharge nozzle moves in a
spiral form toward an outer periphery from the center of the
substrate or inwards from the outer periphery, the following
relation is established:
d.sub.f[m].times.p[m].times.v[m/s].apprxeq..pi.(r[m]).sup.2q[m/s]
(7) wherein the desired average liquid film thickness is assumed to
be d.sub.f, movement pitch of the discharge nozzle of the diameter
direction per one rotation of the substrate in an outermost
periphery is p, the discharge hole radius of the solution discharge
nozzle is r, and a relative linear velocity of the solution
discharge nozzle with respect to the substrate in the outermost
periphery is v.
When this equation is organized with respect to q, the following
relation can be obtained: q=d.sub.f.times.p.times.v/.pi.r.sup.2
(8)
Note that the distance h may be in any region within the range
obtained by the equation (4). To simply obtain the distance in the
apparatus, the distance may also be determined as an intermediate
value between the upper and lower limits. Moreover, when a solution
cut-off function such as a shield plate is disposed between the
solution discharge nozzle and substrate, and the position of the
solution cut-off function is apart from the discharge port of the
solution discharge nozzle by 2 mm or more, it is necessary to
regard the position of solution discharge nozzle as the lower limit
and set h.
Moreover, when the solution is supplied onto the substrate by the
combination of the movement of the column direction of the nozzle
with the movement of the row direction, the method described in the
present embodiment can be applied not only to a circular substrate
but also to a rectangular substrate.
Second Embodiment
For a second embodiment, in the coating method using the coating
apparatus shown in FIG. 1, supply amount correction will be
described with respect to a liquid line discharged, supplied, and
formed on the substrate while linearly moving the nozzle.
The liquid film was prepared under the same conditions as that of
the first embodiment, and further the solvent was dried/removed to
form the solid film. The solvent in the liquid film was dried in
the same manner as in the first embodiment.
Prior-art control of the movement and discharge speeds of the
solution discharge nozzle was executed along a time axis under the
control of PID. This control is fed back so that the movement and
discharge speeds of the solution discharge nozzle indicate the set
values. Moreover, when one line is drawn by the discharged
solution, the control was fed back with respect to a front part of
the solution discharge nozzle in a proceeding direction. However, a
real uniform film cannot be obtained only with this control method.
Preferably a control is executed to make a correction between
adjacent lines.
For example, in the related art, when the PID control is executed
with respect to deviations of the discharge and movement speeds, as
shown in FIG. 10, the film thickness of the liquid film formed on
the substrate with respect to the discharge position of the
solution changes. Note that the liquid film thickness in FIG. 10 is
exchanged from a supply amount to the discharge position and
obtained in consideration of the spread of the solution discharged
onto the substrate.
When the supply amounts of the solution to the discharge positions
are compared in the regions disposed adjacent to each other, the
supply amount changes substantially in the same track. As a result,
as shown by a broken line of FIG. 12, there is a problem that the
film thickness variation is generated along the column direction of
the solution discharge nozzle in the finally formed solid film.
To solve the problem, the method of the present embodiment
comprises: storing a deviation amount of the supply amount; and
obtaining the deviation of the supply amount with respect to the
discharge position, when one line is drawn with the discharged
solution in the column direction. The liquid film thickness
(corresponding to the supply amount) with respect to the discharge
position at this time is shown by a solid line in FIG. 11. Note
that the liquid film thickness in FIG. 11 is exchanged from the
supply amount to the discharge position and obtained in
consideration of the spread of the solution discharged onto the
solution. Also noted that the deviation amount of the supply amount
is generated, for example, by deviation of the discharge speed from
the solution discharge nozzle, and deviation of the movement speed
of the solution discharge nozzle.
Moreover, a discharge amount in an arbitrary position in a region
(second column) disposed adjacent to a track (first column) in
which the deviation amount of the supply amount is obtained is
controlled so as to compensate for the deviation amount of the
supply amount obtained in the adjacent discharge position. The
supply amount of the solution is controlled by controlling at least
one of the discharge speed and the movement speed of the solution
discharge nozzle. In the adjacent discharge region, a fluctuation
of the liquid film thickness is shown by a broken line in FIG.
11.
As a result, since the directions of fluctuations of the liquid
film thickness are reverse to each other in the adjacent lines, the
fluctuations are offset and the uniform liquid film thickness can
be obtained. As a result, the film thickness of the solid film
obtained after removing the solvent in the liquid film is flat,
irrespective of the discharge position, as shown by a solid line in
FIG. 12.
Note that the deviation amount of the discharge speed can be
measured, for example, by monitoring the change of discharge
pressure. Moreover, the deviation amount of the movement speed of
the solution discharge nozzle can be obtained as a differential
value with respect to time, when position information of the nozzle
is obtained with a laser interferometer.
Note that the present embodiment can of course be applied to a
method comprising: rotating the substrate; moving the solution
discharge nozzle in the diameter direction of the substrate; and
discharging the solution in a spiral form onto the substrate to
form the liquid film. In this case, the deviation of the discharge
speed of the solution from the solution discharge nozzle, the
deviation of the movement speed of the solution discharge nozzle,
and the deviation of the rotation speed of the substrate are
measured to obtain the deviation of the supply amount. Moreover, to
supply the solution into a first position of the substrate from the
solution discharge nozzle, the supply amount of the solution
supplied to the first position is controlled so as to compensate
for the deviation amount in the second position in which the
solution has already been discharged and which is disposed adjacent
to the first discharge position in the diameter direction of the
substrate. The solution supply amount is controlled by controlling
at least one of the discharge speed of the solution from the
solution discharge nozzle, movement speed of the solution discharge
nozzle, and rotation speed of the substrate.
Moreover, the substrate may also be dried using only a baker.
Furthermore, the substrate may be rotated, and air blown one's it
to dry it.
Furthermore, to supply the solution onto the substrate by the
combination of the movement of the column direction of the nozzle
with the movement of the row direction, the method described in the
present embodiment can be applied not only to a circular substrate
but also to a rectangular substrate.
Third Embodiment
FIGS. 13A, 13B are diagrams showing a schematic constitution of a
liquid film forming apparatus according to a third embodiment of
the present invention. FIG. 13A is a side view of the apparatus and
FIG. 13B is a plan view of the apparatus.
As shown in FIGS. 13A, 13B, a substrate 120 is horizontally
disposed on a substrate driving system 121. Above the substrate
120, a solution discharge nozzle 122, and a nozzle driving system
123 for reciprocating/moving the nozzle 122 are disposed above the
substrate 120. The solution discharge nozzle 122 is controlled so
as to discharge the solution and to reciprocate/move
leftwards/rightwards along a sheet surface (this direction is
regarded as the column direction) above the substrate 120, and
shield plates 124a, 124b disposed in a space between the substrate
120 and solution discharge nozzle 122 by the nozzle driving system
123.
Every time the solution discharge nozzle 122 moves in one direction
above the substrate 120, the substrate 120 is controlled so as to
move a predetermined pitch in a predetermined row direction
backwards or forwards by the substrate driving system 121. As shown
in FIG. 14, when this operation is repeated, the track of the
discharge position of the solution discharged onto the substrate
120 forms a line shown by a numeral number 131. The track 131 of
the discharge position is linear, and the linearly supplied
solution spreads on a basis of a reach position on the substrate by
fluidity of the solution, and is connected to the adjacent liquid
line to finally form one liquid film. For this, viscosity of the
solution, and movement pitch of the row direction are determined
beforehand.
The shield plates 124a, 124b disposed in the space between the
substrate 120 and solution discharge nozzle 122 move along an outer
edge of the substrate 120 by a cut-off mechanism driving system
126, and arms 125a, 125b, stop discharge of solution 127 from the
solution discharge nozzle 122, thus prevent the solution from
reaching the substrate 120.
In a related-art method for coating a circular substrate, the
column direction positions of the shield plates 124, that is, a
coating start side cut-off position L.sub.s and coating end side
cut-off position L.sub.eare determined as follows, assuming that a
substrate origin is 0 and using a radius r of the substrate, edge
cut width (distance between a substrate edge and liquid film edge
forming position) d, and distance X from the liquid line of the
solution from the solution discharge nozzle:
|L.sub.s|=|L.sub.e|=((r-d).sup.2-x.sup.2).sup.0.5 (9)
FIGS. 15A, 15B schematically show the reach position of the
solution actually cut off at this time on the substrate. The
solution discharge nozzle 122 moves forwards in an arrow direction
at v (m/sec). On the other hand, it is assumed that the discharge
speed of the solution 127 from the nozzle 122 is q (m/sec).
Further, it is assumed that the distance between the shield plate
and substrate (height of cut off of the solution on the basis of
the substrate) is z (m). To usually apply the diluted solution with
this coating apparatus, the discharge speed is about q=5 to 15
m/sec, and distance is about z=0.001 to 0.005 m. Since a distance z
between the discharge port of the solution discharge nozzle 122 and
the substrate 120 is very small as compared with the discharge
speed, the speed change in the discharge distance can be assumed to
be substantially 0. Errors .DELTA.L.sub.1 and .DELTA.L.sub.2 of the
solution reach position onto the substrate from a cut-off position
under this condition can be represented as follows:
|.DELTA.L.sub.1|=|.DELTA.L.sub.2|=vz/q (10)
When the movement speed of the solution discharge nozzle is v=1
m/sec, the discharge speed is q=5 m/s, and z=0.003 m, the errors
are as follows: |.DELTA.L.sub.1|=|.DELTA.L.sub.2|=0.6 mm (11)
Therefore, a generated difference of the edges of the solutions
drawn adjacent to each other is about 1.2 mm with the rectangular
substrate. To coat the circular substrate, a coat film profile in
which the edges are further disordered is obtained as shown in FIG.
16.
On the other hand, in the present embodiment, when a liquid line
proceeding direction is set to +, fine adjustment is made so as to
shift cut-off positions on supply start and end sides from the
position determined by the equation (9) by -vz/q. Thereby, the
liquid film can be formed along a substrate contour shown in FIG.
17.
The solution supplied onto the substrate spreads by fluidity and
forms a liquid film. At this stage, the edge of the liquid film can
have an edge profile along the substrate.
The liquid film prepared with the edge profile along the substrate
may be rotated centering on the substrate, so that the liquid film
can be leveled. Moreover, when the substrate is rotated and dried
in a drying step, the solvent can be evaporated from the liquid
film in a outer peripheral portion with good balance, and the film
thickness variation generated by evaporation can be minimized.
The above-described effect is an effect obtained by forming an edge
portion along the substrate. When the substrate is rotated, a
centrifugal force applied to the liquid film can equally be
scattered in the liquid film edge as shown in FIG. 18A, and the
effect can be obtained. With a zigzag edge as in the related art,
as shown in FIG. 18B, the centrifugal force is concentrated in a
projecting portion of the liquid film, and therefore there is a
problem that the liquid flows toward the outside of the substrate
from this portion.
Note that a method of removing the solvent from the liquid film may
comprise: exposing the substrate on which the liquid film is formed
to an atmosphere of ethyl lactate as that of the solvent included
in the liquid film to level the liquid film; subsequently moving
the substrate into the pressure reduction chamber; reducing the
pressure; removing the solvent in the state held at the pressure in
the vicinity of the saturated vapor pressure of ethyl lactate;
further returning the pressure to normal pressure and thereafter
conveying the substrate out of the pressure reduction chamber; and
heating the substrate at 140.degree. C. on a hot plate to remove
the solvent form the film. Alternatively, the solvent may also be
removed by directly heating the substrate, without exposing it to
reduced pressure.
In the present embodiment, the correction with respect to the
circular substrate has been described, but when a similar
correction is made in the coating of a mask for exposure of a
rectangular substrate, such as a liquid crystal substrate, it is
possible to form a liquid film having an edge along the substrate
edge. Also for a rectangular substrate, when the proceeding
direction of the solution discharge nozzle is set to +, the cut-off
positions on the supply start and end sides may be matched with
positions obtained by shifting the cut-off position by the shield
plate from the liquid film edge forming position formed in the edge
of the rectangular substrate at a constant interval by -vz/q.
Moreover, in addition to the shield plates shown in FIGS. 13A, 13B,
the following cut-off mechanisms for preventing the solution from
reaching the substrate are considered:
(i) a mechanism for spraying gas to change the track of the liquid,
and collecting the solution in a recovery portion disposed in an
opposite position; and
(ii) a mechanism for sucking the discharged solution to change the
track, and collecting the liquid into a liquid recovery
portion.
One example of a liquid film forming apparatus including a
mechanism different from a gas cut-off mechanism shown in FIGS.
13A, 13B is shown in FIGS. 19A, 19B. As shown in FIGS. 19A, 19B,
the present apparatus includes gas emission portions 184a, 184b for
emitting gas to the discharged solution, and solution suction
portions 185a, 185b for recovering the solution by suction, and a
system including both the cut-off mechanisms (i) and (ii) is used.
Note that the shield plates 124a, 124b are disposed to prevent the
solution which cannot be cut off by the gas emission portions 184a,
184b and solution suction portions 185a, 185b from discharging onto
the substrate.
For the driving method, the same control as that of the apparatus
shown in FIGS. 13A, 13B is executed, but the distance z is treated
as a distance between the gas emission portions 184a, 184b for
spraying the gas to cut off the solution and the substrate 120.
Moreover, to supply the solution onto the substrate by the
combination of the movement of the column direction of the nozzle
with the movement in the row direction, the method described in the
present embodiment can be applied not only to a circular substrate
but also to a rectangular substrate.
Fourth Embodiment
FIGS. 20A, 20B, 21A, 21B are explanatory views of problems
according to a fourth embodiment of the present invention, and are
explanatory views of problems generated when the solution discharge
nozzle turns back along the contour of the circular substrate to
form the coat film as shown in FIG. 1.
The solution linearly discharged onto the substrate from the
solution discharge nozzle is regarded as the liquid line. Moreover,
when the adjacent liquid lines stick to each other to form the
liquid film, a portion formed by one liquid line is regarded as a
unit liquid film.
FIGS. 20A, 20B schematically show a spread state of the liquid line
applied in a first column at a coating time of a second column, and
boundary of the unit liquid film in the finally obtained liquid
film in a coating start/end portion at a time of preparation of the
liquid film using the coating apparatus of FIG. 1. FIGS. 21A, 21B
schematically show the spread state of the liquid line applied in
the first column at the coating time of the second column, and
boundary of the unit coat film in the finally obtained liquid film
in the vicinity of a substrate center.
In the coating start and end portions, the nozzle movement distance
in the column direction is short. A time from when the coating of
the first column ends and the solution supply to the substrate is
temporarily discontinued until the coating of the second column
starts and the solution supply to the substrate is restarted
(column direction coating time interval) is short as compared with
the coating of the substrate center portion having substantially
the same diameter as that of the substrate. This time difference
gives a difference to the spread of the solution line of the first
column in applying the solution line of the second column.
As shown in FIG. 20A, in the vicinity of the coating start and end,
the spread of a liquid line 192 of the first column at the coating
time of the second column is insufficient. Therefore, as shown in
FIG. 20B, a boundary B.sub.1 of unit liquid films 193, 194 is
determined on a discharge position P.sub.12 side of the second
column slightly from a center line C.sub.1 of a discharge position
P.sub.11 of the first column and discharge position P.sub.12 of the
second column. In FIG. 20B, an interval between the center line
C.sub.1 and position P.sub.12 is set to SL1.
However, in the vicinity of the center, as shown in FIG. 21A, since
the column direction coating time interval is large, a liquid line
195 of the first column considerably spreads at the coating time of
the second column. Therefore, as shown in FIG. 21B, a boundary
B.sub.2 of unit liquid films 196, 197 is determined further on the
discharge position P.sub.12 side of the second column as compared
with the vicinity of the coating start and end. In FIG. 21B, an
interval between the center line C.sub.2 and position P.sub.22 is
set to SL2 (SL2>SL1).
Such difference of the boundary position of the unit liquid film is
a cause of deterioration of film thickness uniformity. Since the
boundary of the unit liquid film shifts toward a start point side
from the center in the coating start and end portions, a finally
obtained amount of solid content value apparently moves on the
start point side. Therefore, a problem occurs that the solid film
is thick on the coating start side and thin on the end side. In
FIG. 22, plotted triangular marks indicate a relative film
thickness with respect to the film thickness of the substrate
center observed in related-art coating.
When the solution supply amount proportional to an inverse number
of the relative film thickness is given to the corresponding column
based on the relative film thickness plotted by the triangular
marks of FIG. 22, the film thickness uniformity in the row
direction can be enhanced. The solution supply amount is adjusted
by setting the discharge speed from the solution discharge nozzle
to a value obtained by multiplying the related-art discharge speed
by the inverse number of the relative film thickness obtained in
the related-art coating method as a coefficient. Results of the
relative film thickness obtained by the method of the present
embodiment are shown by circular marks of FIG. 22. A uniform film
thickness can be obtained in the whole row direction of the
substrate.
The present embodiment is characterized in that the solution supply
amount to the substrate in the coating start vicinity is set to be
smaller than in the center portion, and that the solution supply
amount to the substrate in the coating end vicinity is set to be
larger than in the center portion. Therefore, the effects of the
present embodiment can also be achieved by the following
control.
(1) The discharge speed from the solution discharge nozzle is
changed in proportion to the inverse number of the relative film
thickness. Note that the same value as that in the related art is
set for other conditions such as the column-direction movement
speed and row-direction movement pitch of the solution discharge
nozzle.
As shown in FIG. 22, the solid film is thick on the liquid film
forming start side, and thin on the liquid film forming end side.
Therefore, the discharge speed in moving the nozzle in the column
direction is set to be smaller than the discharge speed of the
middle position of the substrate in the vicinity of the liquid film
forming start position, and set to be larger than the discharge
speed of the middle position of the substrate in the vicinity of
the liquid film forming end position.
(2) The row-direction movement pitch of the solution discharge
nozzle is changed in proportion to the row-direction relative film
thickness. Note that the same value as that in the related art is
set the for other conditions such as the column-direction movement
speed and discharge speed of the solution discharge nozzle.
As shown in FIG. 22, the solid film is thick on the liquid film
forming start side, and is thin on the liquid film forming end
side. Therefore, the row-direction movement distance in moving the
nozzle in the row direction is set to be larger than the
row-direction movement distance of the middle position of the
substrate in the vicinity of the liquid film forming start
position, and set to be smaller than the row-direction movement
distance of the middle-position of the substrate in the vicinity of
the liquid film forming end position.
(3) The movement of the solution discharge nozzle in a state in
which the solution is not supplied to the substrate is controlled
to adjust time. Preferably, an adjustment speed is adjusted, when
the solution discharge nozzle moves in the row direction.
Alternatively, the adjustment speed at the column-direction
movement time of the nozzle is adjusted. Moreover, the adjustment
speed in the row and column-directions movement time may also be
controlled. To decrease the time interval, the adjustment speed may
be increased. To lengthen the time interval, the adjustment speed
may be decreased. Note that the adjustment of the adjustment speed
also comprises: temporarily stopping the movement of the
nozzle.
In the present embodiment, the coating condition is set on the
basis of the film thickness distribution of the film coated in the
related-art method, but this is not limited. The setting method
comprises: discharging the solution through the nozzle; supplying
one coating line onto the substrate; observing the spread of the
line in the row direction by a CCD camera or video; and obtaining a
speed of spread of the liquid line. On the other hand, a
column-direction coating time interval generated in drawing the
line with the coating apparatus is measured or obtained from
specifications by desk calculation work. The above-described spread
amount and column-direction coating time interval are obtained. In
this case, the condition is easily determined by the method (3).
Moreover, with the adjustment in the method (1), the discharge
speed in coating each column may be obtained. With the adjustment
in the method (2), the movement pitch of the row direction may be
determined.
The present invention is not limited to the above-described
embodiments, and can variously be modified within a range of the
scope in an implementation stage. For example, the liquid film
forming method described above in the respective embodiments can be
applied to a semiconductor process including the coating of a
reflection preventive agent, or resist agent for use in a
lithography process, and the coating of low or high dielectric
material, and to any other film forming process including an
ornamental process such as plating.
Fifth Embodment
In a fifth embodiment, a semiconductor substrate having a diameter
(f)=200 mm was used, and a photoresist solution for chemical
amplification was used as one concrete example in the solution.
Here, it is assumed that the photoresist solution for chemical
amplification includes a solid content of 3.0%. This solid content
indicates a ratio of the solid content included in the solution of
the photoresist. The solid content remains as a solid film after a
drying and baking treatment. Moreover, it is assumed that a film to
be processed (e.g., insulating film) is formed on a semiconductor
substrate beforehand by a known method.
First, the substrate is introduced into a scan coating treatment
unit, and laid and fixed on a stage.
Thereafter, while a solution A is discharged through a nozzle for
solution supply, the nozzle is reciprocated/moved along a
column-direction at a speed of 1 m/sec by a nozzle driving unit.
Moreover, the stage is simultaneously moved in an row-direction at
a pitch interval of 0.6 mm by a stage driving unit. Here, the whole
surface (=plane) of the substrate is coated with the solution A,
and the liquid film is formed with a film thickness of about 10
.mu.m. At this time, the concave/convex portion was formed in the
liquid film on the substrate at a flatness of about 10
.mu.m.+-.10%. Note that the same degree of concave/convex portion
is observed in the liquid on the substrate even with the use of
meniscus coating using the capillary phenomenon.
Subsequently, a leveling treatment is performed to flat the liquid
film on the substrate. Usually after the liquid film is formed on
the substrate, the surface of the liquid film is not completely
smooth as described above, and the concave/convex portion exists
because of the fluctuation of the discharge amount in discharging
the solution. To solve the problem, if necessary, first the
leveling treatment is performed to flat the surface of the liquid
film. Thereafter, the drying treatment is carried out to vaporize
the solvent of the photoresist solution constituting the liquid
film, and a photoresist coat film including the solid content is
formed.
In the present embodiment, in one example, a leveling/drying
treatment apparatus 200 shown in FIG. 23 is used to subject the
liquid film 16 to the leveling and drying treatment, and a series
of treatments is performed so as to form a photoresist film which
has a uniform thickness and whose surface is flatted over the whole
surface of the substrate 11.
The leveling/drying treatment apparatus 200 is constituted by
integrally including a function required for the leveling and
drying treatment, so that the treatment is carried out in the same
chamber. The constitution and function of the leveling/drying
treatment apparatus 200 will be described hereinafter with
reference to FIG. 23.
The leveling/drying treatment apparatus 200 includes a chamber 201
in which the substrate 11 (e.g., semiconductor substrate having a
diameter .(f)=200 nm) is contained, an gas control unit 202, and an
exhaust unit 203 which exhausts the atmosphere in the chamber 201.
The gas control unit 202 mixes inactive gas for dilution (e.g.,
N.sub.2 gas) and solvent gas at a predetermined ratio, and supplies
gas including the solvent at a desired concentration into the
chamber 201. This solvent is the same as that included in the
resist solution.
Here, a stage 205 on which the substrate 11 is laid and fixed is
disposed in the chamber 201. A temperature control plate 206 for
adjusting temperature distribution of the substrate 11 is disposed
in a position under the stage 205.
The temperature control plate 206 can independently control the
temperature of a plurality of regions of the substrate 11. FIG. 24
shows a constitution of the temperature control plate according to
the present embodiment. As shown in FIG. 24, the temperature
control plate 206 includes a middle plate 206a and peripheral edge
plate 206b. The middle plate 206a and peripheral edge plate 206b
independently control the temperature of the regions of the
peripheral edge portion and middle portion of the substrate 11.
Moreover, the gas control unit 202 includes valves for gas supply
V.sub.1 to V.sub.3. The flow rate of inactive gas for dilution
(e.g., N.sub.2 gas) is controlled by adjustment of opening of the
valve V.sub.1. Moreover, the flow rate is controlled by the
adjustment of the flow rate of solvent gas and opening of the valve
V.sub.2. When the openings of the valves V.sub.1 and V.sub.2 are
adjusted, two gases are mixed at a predetermined density. The
opening of the valve V.sub.3 is adjusted to control the supply
amount of mixed gas into the chamber 201.
The exhaust unit 203 has a vacuum pump and valve V.sub.4. The valve
V.sub.4 is inserted into a pipe which connects the chamber 201 to
the vacuum pump. When the opening of the valve V.sub.4 is adjusted,
air current amount and pressure of the atmosphere in the chamber
201 are adjusted. Furthermore, the leveling/drying treatment
apparatus 200 includes an optical system for film thickness
measurement 207 to measure the film thickness of the liquid film 16
in each treatment step. The optical system for film thickness
measurement 207 mainly includes a light irradiation portion 208 and
light receiving portion 209. The light irradiation portion 208 is
constituted of a light source which emits a light having a
wavelength in a visible region. The light receiving portion 209 is
constituted of a CCD camera. Moreover, a plurality of sets of light
sources 208 and light receiving portions 209 are disposed so as to
measure the film thickness of the liquid film 16 in a plurality of
positions on the substrate 11.
Additionally, the leveling/drying treatment apparatus 200 includes
an analysis unit 210. The analysis unit 210 is connected to the gas
control unit 202, temperature control plate 206, and optical system
for film thickness measurement 207.
The light source 208 irradiates the liquid film 16 with visible
light. The light receiving portion 209 receives the reflected light
and measures light intensity. The analysis unit 210 calculates the
film thickness of the liquid film 16 from the intensity of the
reflected light. Moreover, the analysis unit 210 controls the
concentration of the solvent in the gas supplied into the chamber
201, pressure in the chamber 201, temperature of the substrate 11,
and exhaust in the chamber 201 in accordance with the calculated
film thickness of the liquid film 16.
The leveling/drying treatment apparatus 200 constituted as
described above is used to first perform the leveling treatment so
that the film thickness of the liquid film 16 is uniform and the
surface of the film is flatted in the whole surface of the
substrate 11.
Conditions such as the temperature of the substrate at a leveling
treatment time, flow rate of the air current in the treatment
apparatus, exhaust, concentration of the solvent in the gas, and
pressure are changed, and the substrate for test is used to is
perform the leveling treatment. During the leveling treatment, a
film thickness difference of the center and peripheral edge regions
of the substrate are observed. A condition on which the difference
of the film thickness measured in each region is small is set to an
initial condition of the leveling treatment. The film thickness
difference is observed by irradiating each region with light and
counting the number of interference fringes of the reflected light.
When the number of interference fringes is small, the film
thickness difference is small.
The procedure of the leveling treatment will concretely be
described with reference to FIGS. 25, and 26A to 26C. FIG. 26A is a
diagram showing a change of the film thickness of the liquid film
in each position on the substrate with time in the leveling
treatment according to the fifth embodiment, FIG. 26B is a diagram
showing a change of solvent concentration in gas supplied into the
chamber with time in the leveling treatment according to the fifth
embodiment, and FIG. 26C is a diagram showing a change of
temperature of middle and peripheral edge plates in the leveling
treatment according to the fifth embodiment.
First, the substrate 11 is conveyed into the chamber 201 of the
leveling/drying treatment apparatus 200, and laid and fixed onto
the stage 205. At this time, temperature T.sub.c of the middle
plate 206a disposed in the stage 205, and temperature T.sub.r of
the peripheral edge plate 206b are set around room temperature
(e.g., 23.degree. C.).
Thereafter, the leveling treatment is started to flat the surface
of the liquid film 16. The openings of the valves for gas supply
V.sub.1 to V.sub.3 of the gas control unit 202 are adjusted, and a
mixture gas is generated by mixing the solvent gas and gas for
dilution in a predetermined concentration. The mixture gas is
supplied into the chamber 201, and the atmosphere including the
solvent is formed in the chamber 201. In the present embodiment,
the concentration of the solvent in the mixture gas at the start
time of the leveling treatment is 100%.
The same solvent as that constituting the liquid film 16, or a
similar solvent is used in the solvent gas. When the liquid film 16
is exposed to the atmosphere including the solvent, the fluidity
inside the liquid film 16 is promoted, and the surface tension can
be used to smooth the surface.
In the present embodiment, in the process of the leveling
treatment, the film thickness of the liquid film 16 is measured, a
necessary parameter is selected from parameters relating to the
treatment in accordance with measurement result, and the value of
the parameter is controlled. At this time, the value of the
selected parameter is controlled. By this control, during the
leveling treatment, the film thickness difference of the liquid
film 16 is controlled over the whole surface of the substrate 11.
Here, in one example, as the parameter, the concentration of the
solvent in the chamber 201, and temperature distribution of the
substrate 11 are selected, and the values of these parameters are
controlled.
In this case, in the present embodiment, during the leveling
treatment, the optical system for film thickness measurement 207
and analysis unit 210 are used to measure the film thickness of the
liquid film 16 in a plurality of positions in the peripheral edge
from the middle portion of the substrate 11. At this time, the film
thickness of the liquid film 16 is measured in a plurality of
points P.sub.1, P.sub.2, P.sub.3 on the substrate shown in FIG.
25.
FIG. 25 shows a sectional view of the substrate 11 and liquid film
16. Here, the point P.sub.1 is an arbitrary position on a middle
portion R.sub.c of the substrate 11, point P.sub.3 is an arbitrary
position on a peripheral edge R.sub.r of the substrate 11, and
P.sub.2 is an arbitrary position between P.sub.1 and P.sub.3 in the
substrate 11.
Note that in the present embodiment, the peripheral edge R.sub.r
indicates a region in a width corresponding to about 5% of a
substrate diameter from the edge (=endmost portion) of the
substrate. Therefore, when the diameter (f) of the substrate is 200
mm, the peripheral edge indicates the region in a width of 10 mm
from the edge (=endmost portion).
In the process of the leveling treatment, in the leveling/drying
treatment apparatus 200, the optical system for film thickness
measurement 207 is used to measure the film thickness of the liquid
film 16 in the respective points P.sub.1, P.sub.2, P.sub.3.
Moreover, in order to inhibit the film thickness in each point from
increasing/decreasing, the analysis unit 210 sends an instruction
to the gas control unit 202 and temperature control plate 206, and
the concentration of the solvent in the chamber 201 and temperature
distribution of the substrate 11 are controlled.
The leveling treatment will concretely be described hereinafter
with reference to FIGS. 26A to 26C.
As shown in FIG. 26A, immediately after the leveling treatment is
started, the film thickness of the liquid film 16 in the respective
points P.sub.1, P.sub.2, P.sub.3 on the substrate 11largely
deviate. Thereafter, on the basis of the preset film thickness
(e.g., 10 .mu.m), in the respective points P.sub.1, P.sub.2,
P.sub.3 on the substrate 11, the concentration of the solvent in
the chamber 201 and temperature distribution of the substrate 11are
controlled so that the film thickness of the liquid film 16 is
within a given range.
Concretely, as shown in FIG. 26B, the concentration of the solvent
in the mixture gas supplied into the chamber 201 is 100%
immediately after the start of the leveling treatment. Thereafter,
the concentration of the solvent in the mixture gas is gradually
reduced to 60%. Here, the surface of the liquid film 16 is flatted,
and the concentration of the solvent in the chamber 201 is
gradually decreased so that the film thickness difference of the
liquid film 16 is within a substantially constant range in the
respective points P.sub.1, P.sub.2, P.sub.3 on the substrate
11.
Moreover, while the concentration of the solvent in the atmosphere
is controlled, the temperature of the temperature control plate 206
is simultaneously controlled independently in the middle and
peripheral edge portions of the substrate 11. Concretely, when the
substrate 11 is laid on the stage 205, the whole temperature
control plate 206 is set to a substantially constant temperature.
Thereafter, in the process of the leveling treatment, the
temperature is controlled independently in the positions of the
middle portion corresponding to the point P.sub.1 and the
peripheral edge corresponding to the point P.sub.3.
Here, in one example, first the temperature T.sub.c of the middle
plate 206a and temperature T.sub.r of the peripheral edge plate
206b are set at temperature of about 23.degree. C., before the
substrate 11 is laid on the stage 205. Thereafter, as shown in FIG.
26C, the temperature T.sub.c of the middle plate 206a is kept at
23.degree. C. The temperature T.sub.r of the peripheral edge plate
206b is lowered to about 15.degree. C. During the leveling
treatment, the temperature T.sub.c of the middle plate 206a is
controlled to be kept at 15.degree. C. During the leveling
treatment, the temperature of the peripheral edge R.sub.r of the
substrate 11 is set to be lower than that of the middle portion
R.sub.c. By this temperature distribution, the solid content is
inhibited from flowing in a direction of the middle portion R.sub.c
from the peripheral edge R.sub.r, and the film thickness
distribution is within a constant range.
Thereafter, when the film thickness of the liquid film 16 in the
respective points P.sub.1, P.sub.2, P.sub.3 is within the given
range on the basis of the preset film thickness, the leveling
treatment ends. The leveling treatment ends, when all the valves
V.sub.1 to V.sub.3 of the gas supply system are closed and the
supply of the gas into the chamber 201 is stopped.
Note that in one example the film thickness of the liquid film 16
in the respective points P.sub.1, P.sub.2, P.sub.3 is within a
range of about .+-.0.5% on the basis of 10 .mu.m and at this time
the leveling treatment of the present embodiment ends.
Subsequently, the drying treatment is performed so as to vaporize
the solvent of the liquid film 16 in the state in which the
substrate 11 is laid on the stage 205 in the chamber 201. This
drying treatment comprises: vaporizing the solvent in the liquid
film 16; and leaving the solid content in the liquid film 16 on the
substrate 11 to form the solid film on the substrate. As one
example, the present embodiment comprises: vaporizing the
photoresist solution by a pressure reduction treatment; and forming
the photoresist film having a film thickness of about 400 nm as the
solid film. Here, after the supply of the mixture gas into the
chamber 201 is stopped, first a vacuum pump 204 is used to exhaust
the atmosphere in the chamber 201 at a predetermined rate.
For the respective conditions such as the temperature of the
substrate at the drying treatment time, air current, concentration
of the solvent in the gas supplied into the chamber, and pressure,
while a substrate for test is used to change the respective
conditions beforehand, the film thickness is measured by reflected
light measurement in a plurality of points including at least the
center of the substrate, coating start position, and coating end
position. Even in the process of the decrease of the film thickness
of the liquid film, a condition at a time of reduction of the
interference fringes of the reflected light may be determined from
these results.
In the present embodiment, in the process of the drying treatment,
the film thickness of the liquid film 16 is measured and monitored.
Additionally, the necessary parameter is selected from the
parameters relating to the treatment, and the value of the
parameter is controlled. At this time, while the value of the
selected parameter is controlled, and the drying treatment is
performed, the film thickness difference of the liquid film 16 is
controlled to be within the predetermined range over the whole
surface of the substrate 11, the solvent is vaporized, and finally
the solid film having a thickness of 400 nm is formed. Here, in one
example, the temperature distribution of the substrate 11 is
selected as the parameter, and the value is controlled.
In this case, in the present embodiment, during the drying
treatment, the optical system for film thickness measurement 207
and analysis unit 210 are used to measure the film thickness of the
liquid film in the respective points P.sub.1 to P.sub.3 in the same
manner as in the leveling treatment. At this time, the analysis
unit 210 controls each parameter so that the difference of the film
thickness in these points P.sub.1 to P3 is within the predetermined
range. In the present embodiment, in one example, the value of the
parameter is controlled so that the film thickness of the points
P.sub.1 to P.sub.3 is within a range of an average film thickness
value .+-.0.5%.
Here, the drying treatment will concretely be described with
reference to FIGS. 27A to 27C. FIG. 27A is a diagram showing the
change of the film thickness of the liquid film in each position on
the substrate with time in the leveling and drying treatments
according to the fifth embodiment, FIG. 27B is a diagram showing
the change of pressure in the chamber with time in the leveling and
drying treatments according to the fifth embodiment, and FIG. 27C
is a diagram showing the change of temperature of the middle and
peripheral edge plates in the leveling and drying treatments
according to the fifth embodiment. Moreover, FIGS. 27A to 27C show
the states of the above-described leveling and drying
treatments.
In the present embodiment, as shown in FIG. 27A, the difference of
the film thickness is controlled to be within the given range, the
drying treatment is carried out until the predetermined film
thickness (e.g., 400 nm) is obtained, and the solvent in the liquid
film 16 is vaporized.
Moreover, in the present embodiment, the drying treatment is
performed in the reduced pressure state in the chamber 201. In
order to vaporize the solvent in the liquid film 16, the vacuum
pump disposed in the exhaust unit 203 is used to exhaust the
atmosphere in the chamber 201 to the outside at -60 Torr/sec.
Concretely, as shown in FIG. 27B, the pressure in the chamber 201
is kept at about 760 Torr during the leveling treatment. At the
drying treatment time, the atmosphere in the chamber is exhausted
at -60 Torr/sec, and pressure is lowered to and kept at about 2
Torr corresponding to the vapor pressure of the solvent.
At this time, in the process of the drying treatment, the
temperature of the substrate 11 is controlled. A case in which the
measured film thickness of the point P.sub.3 tends to be smaller
than that of the peripheral edge will be described. Here, as shown
in FIG. 27C, the temperature T.sub.r of the peripheral edge plate
206b is gradually lowered to about 13.degree. C. from 15.degree. C.
Thereafter, the temperature of the peripheral edge plate 206b is
kept at 13.degree. C. On the other hand, the temperature T.sub.c of
the middle plate is kept at about 23.degree. C. (=room temperature)
in the same manner as in the leveling treatment. During the drying
treatment, the temperature of the peripheral edge of the substrate
11 is set to be lower than that of the middle portion. When the
temperature distribution of the substrate 11 is controlled in this
manner, a vaporization speed of the solvent on the peripheral edge
discharges as compared with the middle portion, and it is possible
to inhibit the solid content from moving into the middle portion
from the peripheral edge.
When the measured film thickness of the point P.sub.3 tends to be
thicker than that of the peripheral edge, the temperature of the
peripheral edge of the substrate 11 is set to be higher than that
of the middle portion. When the temperature distribution of the
substrate 11 is controlled in this manner, the vaporization speed
of the solvent on the middle portion discharges as compared with
that on the middle portion, and it is possible to inhibit the solid
content from moving into the peripheral edge from the middle
portion.
In the present embodiment, the drying treatment ends at a time when
the solvent of the liquid film 16 is sufficiently vaporized and the
film thickness of the liquid film 16 reaches a predetermined film
thickness (e.g., 400 nm) and does not change in the respective
points P.sub.1, P.sub.2, P.sub.3 on the substrate 11.
Subsequently, the substrate 11 is conveyed out of the
leveling/drying treatment apparatus 200, and introduced into a back
treatment portion (not shown). Here, when a heating treatment is
performed at 140.degree. C. for about 50 seconds, the film is
stabilized.
As described above, the coat film of the photoresist with a
thickness of about 400 nm (=film of the solid content included in
the liquid film 16) is formed as the solid film. Here, the effect
of the present embodiment will be described in comparison to the
related-art method with reference to FIGS. 28A to 28C and 29A and
29B. FIG. 28A is a diagram showing the change of the film thickness
of the liquid film in each position on the substrate with time in
the leveling and drying treatments according to the fifth
embodiment, FIG. 28B is a diagram showing the change of the film
thickness of the liquid film in each position on the substrate with
time in the related-art leveling and drying treatments, and FIG.
28C is a diagram showing the change of the film thickness of the
liquid film in each position on the substrate with time in the
related-art leveling and drying treatments. FIGS. 29A, 29B are
diagrams showing the effect of the fifth embodiment.
In the present embodiment, as shown in FIG. 28A, the film thickness
of the liquid film is controlled to be within the given range as
needed during the leveling and drying treatments.
In the related-art method, without controlling the concentration of
the solvent in the chamber 201, and temperature distribution of the
substrate 11, the leveling treatment is performed. Concretely, in
the process of the leveling treatment, the concentration of the
solvent in the gas supplied into the chamber 201 is set to 100% and
kept at this value. Moreover, the temperature of the whole
temperature control plate 206 is set at 23.degree. C., and kept at
this value. Thereafter, the drying treatment is performed so as to
vaporize the solvent in the chamber 201 whose pressure has been
reduced. At this time, in the related-art method, the film
thickness of the liquid film is not measured. Moreover, the
temperature of the temperature control plate is kept constant.
In the related-art method, when the film thickness of the liquid
film 16 is measured in the respective points P.sub.1, P.sub.2,
P.sub.3 during the leveling treatment, as shown in FIG. 28B, the
film thickness decreases in the point P.sub.3 on the substrate 11.
Conversely, it is seen that the film thickness increases in the
point P.sub.1.
Moreover, at the end time of the leveling treatment, the film
thickness of the liquid film 16 in the point P.sub.1 was 18 .mu.m,
and the film thickness of the liquid film 16 in the point P.sub.3
was 2 .mu.m. It is seen that the film thickness difference of the
liquid film 16 is large on the middle portion and peripheral edge
of the substrate 11. In this manner, in the related-art method, the
concave/convex portion in the surface generated in the process of
formation of the liquid film disappears by the leveling treatment,
and the whole film tends to be thick in the middle portion and thin
in the peripheral edge.
Furthermore, thereafter, the drying treatment is performed in the
reduced pressure state. In the related-art drying treatment, when
the solvent of the liquid film is vaporized, the film thickness is
not controlled so as to be within the given range as described
above. Therefore, when the drying treatment is performed, film
thickness sag (=decrease of the film thickness) of the peripheral
edge is further promoted in the process of vaporization of the
solvent, and the solid film is formed.
Another method will next be described. In the same manner as in the
present embodiment, at the leveling treatment time, this method
comprises: measuring and monitoring the film thickness of the
liquid film in the respective points P.sub.1, P.sub.2, P.sub.3;
controlling the concentration of the solvent in the gas supplied
into the chamber 201; and using the temperature control plate to
control the temperature distribution of the substrate. Thereafter,
the film thickness is not measured at the drying treatment time.
Moreover, while the temperature of the temperature control plate is
kept to be constant at 23.degree. C., the solvent is vaporized and
the drying treatment is performed.
In this method, as shown in FIG. 28C, immediately after the end of
the leveling treatment, the film thickness of the liquid film is
flatted over the whole surface, but at the drying treatment time
the film thickness of the point P.sub.3 remarkably decreases as
compared with the point P.sub.1. The finally formed film is flatted
in the middle portion, but the film thickness decreases in the
peripheral edge.
FIG. 29A shows the distribution of the film thickness of the solid
film formed in temperature profiles shown in FIGS. 28A to 28C.
Moreover, FIG. 29B shows the film thickness uniformity of the solid
film. In FIGS. 29A, 29B, A denotes the solid film formed in the
temperature profile shown in FIG. 28A, B denotes the solid film
formed in the temperature profile shown in FIG. 28B, and C denotes
the solid film formed in the temperature profile shown in FIG.
28C.
Note that FIG. 29A is a sectional view of the solid film formed on
the substrate, and shows the change of the film thickness.
Thereby, it is seen that in B, already at the leveling treatment
time, the film thickness of the liquid film largely deviates, and
that a large film thickness difference is generated in the
positions on the peripheral edge (=coordinate: .+-.100) and middle
portion (=coordinate: 0) after the drying treatment. Moreover, in
C, at the leveling treatment time, the film thickness difference is
within the given range in each point, but the film thickness
difference is generated at the drying treatment time, and the film
thickness difference is generated on the peripheral edge and middle
portion.
As shown in FIG. 29B, the film thickness uniformity was 20% in B
and 10% in C. On the other hand, in A, the solid film whose film
thickness is substantially uniform at 400 nm and which has a
flatted state is formed over the whole surface of the substrate.
Moreover, the film thickness uniformity of A is 1.0%, and is
largely enhanced as compared with B and C.
Thereby, when the film thickness of the liquid film at each
treatment time is measured and monitored and controlled to be
within the given range as needed, as in the present embodiment, a
solid film having a flat surface and uniform film thickness can be
formed.
As described above, in the present embodiment, during the processes
of the leveling and drying treatments, the change of the film
thickness of the liquid film 16 is monitored, and each parameter
can be adjusted to have the appropriate value while each treatment
is performed. Therefore, in the present embodiment, it is possible
to obtain a high-precision (i.e., flat) film thickness distribution
in the solid film (e.g., photoresist film).
For example, as a result of the monitoring, in the leveling
treatment, when the concentration of the solvent in the gas
supplied into the chamber is gradually lowered during the treatment
step, the solvent can be prevented from being unnecessarily applied
to the surface of the liquid film 16 and the film thickness
distribution can be prevented from being disordered. Moreover, in
the drying treatment, the temperature difference between the
peripheral edge and middle portion of the substrate 11 is
controlled, and thereby the solid content movement is prevented
from being caused by the difference in physical properties of the
liquid film between the middle portion and peripheral edge of the
substrate with the progress of the drying, that is, vaporization of
the solvent.
The present embodiment can be modified without departing from the
scope of the present invention.
The leveling treatment can be changed as follows. In the present
embodiment, the concentration of the solvent in the chamber 201
during the leveling treatment is uniformed in the chamber 201 as a
treatment container, but this is not limited. For example, a
concentration distribution may be disposed in the plane of the
liquid film 16. In this case, as shown in FIG. 30, a supply port
211 for supplying the gas including the solvent into the chamber
201 may be constituted to be movable in the plane of the liquid
film 16. Moreover, the substrate 11 itself may be constituted so as
to be movable.
In this case, it is possible to adjust the concentration of the
solvent in the gas supplied onto the liquid film surface in
accordance with the film thickness of the liquid film 16 and to
flat the surface. Moreover, with the method for controlling the
film thickness of each point to satisfy the desired value, it is
unnecessary to control all the parameters, such as the
concentration of the solvent and temperature distribution of the
substrate 11, and any one parameter may be controlled.
Moreover, in the present embodiment, in the leveling and drying
treatments, the concentration of the solvent and the temperature
distribution of the temperature control plate are not limited to
the above-described values, and can be changed in accordance with
type of coating solution used, substrate, and coating method.
Furthermore, the solvent for use in the leveling treatment is not
limited to the solvent of the material used in the liquid film 16,
and any material that functions with respect to the liquid film 16
so as to promote the fluidity of the liquid film 16 may be used.
Additionally, a solvent including a surface-active agent which
functions so as to lower the surface tension of the liquid film 16
may also be used.
Moreover, in the present embodiment, the fluidity of the surface is
promoted by adding the solvent to the surface of the liquid film 16
and the leveling is performed, but this is not limited.
In the leveling treatment, the gas including the solvent with the
given concentration is supplied into the chamber 201, and the
temperature control plate 206 is used to control the temperature of
the substrate 11, so that the surface can be flatted.
Here, the leveling treatment will concretely be described with
reference to FIGS. 31A to 31C. FIG. 31A is a diagram showing the
change of the film thickness of the liquid film in each position on
the substrate with time in the leveling treatment according to the
fifth embodiment, FIG. 31B is a diagram showing the change of
solvent concentration in gas supplied into the chamber with time in
the leveling treatment according to the fifth embodiment, and FIG.
31C is a diagram showing the change of temperature of the middle
and peripheral edge plates in the leveling treatment according to
the fifth embodiment.
First, the substrate 11 is conveyed into the chamber 201 of the
leveling/drying treatment apparatus 200, and laid and fixed onto
the stage 205. At this time, the temperature T.sub.c of the middle
plate 206a disposed in the stage 205 is set at 30.degree. C., and
the temperature T.sub.r of the peripheral edge plate 206b is set at
23.degree. C.
Thereafter, the leveling treatment is started so as to flat the
surface of the liquid film 16. At this time, as shown in FIG. 31B,
during the leveling treatment, the concentration of the solvent in
the gas supplied into the chamber 201 is kept constant. For
example, the concentration of the solvent is kept at 50%.
Immediately after the leveling treatment is started, as shown in
FIG. 31C, the film thickness of the liquid film 16 largely deviates
in the respective points P.sub.1, P.sub.2, P.sub.3 on the substrate
11.
Moreover, as shown in FIG. 31C, after the leveling treatment
starts, the temperature T.sub.r of the peripheral edge plate 206b
is lowered to about 30.degree. C. As a result, the temperature of
the middle portion of the substrate varies greatly from that of the
peripheral edge of the substrate.
In this leveling treatment, the temperature of the middle portion
of the substrate 11 is raised, the viscosity of the liquid film 16
is reduced, and the fluidity is further promoted. Thereby, the
surface can be flatted in the same manner as in the case in which
the solvent is supplied to the surface of the liquid film 16.
Furthermore, at this time, the temperature of the peripheral edge
of the substrate 11 is lowered to about 20.degree. C. During the
leveling treatment, the temperature of the peripheral edge of the
substrate 11 is set to be lower than that of the middle portion.
Therefore, it is possible to inhibit the solid content from moving
toward the middle portion from the peripheral edge of the substrate
11.
In the present embodiment, in the drying treatment, the inside of
the chamber 201 is exhausted, and the solvent of the liquid film is
vaporized in this reduced pressure state, but this is not limited,
and can be changed as follows.
For example, in order to promote the vaporization of the solvent,
the air current by the inactive gas (e.g., N.sub.2, Ar) is formed
on the surface of the liquid film 16, and the drying treatment can
be performed. In this case, as shown in FIG. 32, in the
leveling/drying treatment apparatus 200, the gas control unit 202
is used. The inactive gas such as N.sub.2 is fed into the chamber
201 from above the substrate 11, the air current is supplied to the
surface of the liquid film 16 to vaporize the solvent, and the
drying treatment can be performed. Here, as described above, in the
leveling/drying treatment apparatus 200, the temperature control
plate 206 is disposed on the stage 205 on which the substrate 11 is
laid. Moreover, if there is no particular problem, air may be used
in forming the air current.
Note that the supply of gas from above the substrate 11 is not
limited. In the leveling/drying treatment apparatus 200, the gas is
fed into the chamber 201 from below the substrate 11, and may be
exhausted from above the substrate 11. Moreover, the air current
may flow in one direction (transverse direction) with respect to
the surface of the substrate 11. For example, the gas may be
supplied through one end of the substrate 11 and exhausted through
the other end.
Here, this drying treatment will concretely be described with
reference to FIGS. 33A to 33C. FIG. 33A is a diagram showing the
change of the film thickness of the liquid film in each position on
the substrate with time in the leveling and drying treatments
according to the fifth embodiment, FIG. 33B is a diagram showing a
change of a flow rate of N.sub.2 gas supplied into the chamber with
time in the leveling and drying treatments according to the fifth
embodiment, and FIG. 33C is a diagram showing the change of
temperature of the middle and peripheral edge plates in the
leveling and drying treatments according to the fifth embodiment.
FIGS. 33A to 33C continuously show the states of the
above-described leveling and drying treatments.
As shown in FIG. 33A, the leveling treatment is performed, and the
difference of the film thickness of each point is controlled to be
within the given range. Thereafter, the drying treatment is
performed, and the solvent is vaporized until the liquid film 16
obtains a predetermined film thickness (e.g., 400 nm).
After the leveling treatment ends, the drying treatment is
performed. In the drying treatment, the inactive gas (e.g.,
N.sub.2, Ar) is fed into the chamber 201, and the air current is
formed on the surface of the liquid film 16 to vaporize the solvent
in the liquid film. At the drying treatment time, N.sub.2 gas is
supplied into the chamber 201, and an air current is formed in the
surface of the liquid film 16. As shown in FIG. 33B, at the drying
treatment time, the flow rate of the N.sub.2 gas is increased to
about 5 L/min.
Moreover, at this time, in the process of the drying treatment, the
temperature of the substrate 11 is controlled. Here, as shown in
FIG. 33C, the temperature T.sub.c of the middle plate 206a is kept
at about 23.degree. C. as in the leveling treatment time. The
temperature T.sub.r of the peripheral edge plate 206b is gradually
lowered to about 13.degree. C. from 15.degree. C. of the leveling
treatment time. Thereafter, in the process of the drying treatment,
the temperature T.sub.r of the peripheral edge plate 206b is kept
at about 13.degree. C.
In this manner, during the leveling treatment, the temperature of
the peripheral edge of the substrate 11 is set to be lower than
that of the middle portion, and it is possible to reduce the
movement of the solid content toward the middle portion from the
peripheral edge.
In the present embodiment, when the solvent of the liquid film 16
is sufficiently vaporized, and the film thickness of the liquid
film 16 reaches the predetermined film thickness in the respective
points P.sub.1, P.sub.2, P.sub.3 on the substrate 11 and does not
change, the drying treatment is ended.
In the present embodiment, in this case, during the drying
treatment, the flow rate of the air current is changed as needed,
and the film thickness of the liquid film 16 can be inhibited from
being lowered on the peripheral edge of the substrate 11. For
example, the temperature of the peripheral edge of the substrate 11
is lowered, and the temperature difference from the middle portion
is generated. Additionally, the air current may also be increased
toward the end from the initial stage of the drying in accordance
with the film thickness in the respective points P.sub.1, P.sub.2,
P.sub.3 on the substrate 11. In this method, the solid content of
the liquid film moved toward the middle portion from the peripheral
edge of the substrate is pushed back toward the peripheral edge and
the drying may be performed.
Here, this drying treatment will be described with reference to
FIGS. 34A to 34C. FIG. 34A is a diagram showing the change of the
film thickness of the liquid film in each position on the substrate
with time in the leveling and drying treatments according to the
fifth embodiment, FIG. 34B is a diagram showing the change of the
flow rate of N.sub.2 gas supplied into the chamber with time in the
leveling and drying treatments according to the fifth embodiment,
and FIG. 34C is a diagram showing the change of temperature of the
middle and peripheral edge plates in the leveling and drying
treatments according to the fifth embodiment. FIGS. 34A to 34C show
the states of the above-described leveling and drying
treatments.
As shown in FIG. 34A, the leveling treatment is performed, and the
difference of the film thickness is controlled to be within the
given range. After the leveling treatment, the drying treatment is
performed until the liquid film 16 obtains the predetermined film
thickness (e.g., 400 nm).
In the drying treatment, an inactive gas (e.g., N.sub.2, Ar) is fed
into the chamber 201, and an air current is supplied onto the
surface of the liquid film 16 to vaporize the solvent. Concretely,
N.sub.2 gas is fed into the chamber 201, and the air current is
formed over the surface of the liquid film 16. At this time, as
shown in FIG. 34B, the flow rate of the gas is increased to 5 L/min
from the start time of the drying treatment. Thereafter, the flow
rate is substantially kept, and increased to about 2500 L/min in an
index function manner at the point of end.
In the drying treatment, the temperature of the substrate 11 is
controlled. Here, as shown in FIG. 34C, the temperature T.sub.r of
the peripheral edge plate 206b is gradually lowered to about
17.degree. C. from the temperature (=20.degree. C.) of the leveling
treatment time. Thereafter, in the process of the drying treatment,
the temperature T.sub.r is maintained constant. On the other hand,
the temperature T.sub.c of the middle plate is lowered to about
23.degree. C. (=room temperature) from the temperature (=30.degree.
C.) of the leveling treatment time. Thereafter, the temperature
T.sub.c is maintained constant.
In the present embodiment, when the solvent of the liquid film 16
is sufficiently vaporized, and the film thickness of the liquid
film 16 reaches a predetermined film thickness (e.g., 400 nm) in
the respective points P.sub.1, P.sub.2, P.sub.3 on the substrate
11, and does not change, the drying treatment is ended.
Moreover, when an air current is supplied to the liquid film 16 to
perform the drying treatment, a part of the leveling/drying
treatment apparatus 200 is changed, and an air current control
plate 212 may be disposed in the position of the outer periphery of
the substrate 11 as shown in FIG. 35. Since the air current control
wall 212 is disposed in this position, the air current is reduced
on the peripheral edge of the substrate 11, and rapid drying (i.e.,
vaporization of the solvent) can be inhibited. Therefore,
controllability of the film thickness of the liquid film 16 is
enhanced in the peripheral edge of the substrate 11.
In the present embodiment, when the rotation of the substrate is
combined at the drying treatment time, the film thickness
difference of the liquid film is controlled to be within the given
range, and the solvent can be vaporized.
In this case, a part of the leveling/drying treatment apparatus 200
is changed, and a rotation system stage 213 is disposed as shown in
FIG. 36. While the substrate 11 is laid and fixed onto the rotation
system stage 213, the leveling and drying treatments are performed.
Moreover, the rotation system stage 213 is connected to the
analysis unit 210.
The analysis unit 210 sends an indication of a rotation speed to
the rotation system stage 213 based on the measurement result of
the optical system for film thickness measurement 207, and the
rotation speed of the substrate 11 is controlled.
For example, after the leveling treatment, the gas in the chamber
201 is exhausted, and the drying treatment is performed in the
reduced pressure state. During the drying treatment, the substrate
11 starts to be rotated at a predetermined timing. While the
rotation speed of the substrate 11 is increased, the film thickness
of the liquid film 16 is controlled in each point.
This drying treatment will be described with reference to FIGS. 37A
to 37C. FIGS. 37A to 37C continuously show the states of the
above-described leveling and drying treatments.
As shown in FIG. 37A, after the leveling treatment, the difference
of the film thickness in each point is controlled to be within the
given range, the solvent of liquid film 16 is vaporized until a
predetermined film thickness (e.g., 400 nm) is obtained, and the
drying treatment is performed.
At this time, the drying treatment is performed in a reduced
pressure state in the chamber 201. In order to vaporize the solvent
in the liquid film 16, a vacuum pump disposed in the exhaust unit
203 is used to exhaust the atmosphere in the chamber 201 to the
outside at -60 Torr/sec. Concretely, as shown in FIG. 37B, the
pressure in the chamber 201 is kept at about 760 Torr during the
leveling treatment. Thereafter, the atmosphere in the chamber 201
is exhausted at -60 Torr/sec, and pressure in the chamber 201 is
set to about 2 Torr corresponding to the vapor pressure of the
solvent. Moreover, during the drying treatment, the pressure in the
chamber 201 is kept at 2 Torr.
Moreover, as shown in FIG. 37C, the leveling treatment is performed
while the substrate 11 is in a stationary state (=rotation speed of
0 rpm). The substrate 11 is rotated from the middle of the drying
treatment. Towards the end of the drying treatment, the rotation
speed is rapidly increased in the index function manner until the
rotation speed is about 300 rpm.
In this case, the rotation speed of the substrate is increased in
accordance with the film thickness of the liquid film 16, the flow
of the liquid film 16 to the middle portion from the peripheral
edge is inhibited by the centrifugal force, and the solid content
can be inhibited from moving onto the middle portion. Moreover,
this method can also be applied to the drying treatment in which an
air current is supplied, as described above.
This drying treatment will be described with reference to FIGS. 38A
to 38C. FIGS. 38A to 38C show the states of the above-described
leveling and drying treatments. FIG. 38A is a diagram showing the
change of the film thickness of the liquid film in each position on
the substrate with time in the leveling and drying treatments
according to the fifth embodiment, FIG. 38B is a diagram showing
the change of the flow rate of N.sub.2 gas supplied into the
chamber with time in the leveling and drying treatments according
to the fifth embodiment, and FIG. 38C is a diagram showing the
change of the rotation speed of the substrate in the leveling and
drying treatments according to the fifth embodiment.
As shown in FIG. 38A, after the leveling treatment, the difference
in film thickness at each point is controlled to be within a given
range, the solvent of liquid film 16 is vaporized until a
predetermined film thickness (e.g., 400 nm) is obtained, and the
drying treatment is performed.
At this time, after the end of the leveling treatment, an inactive
gas (e.g., N.sub.2, Ar) is fed into the chamber 201, and the air
current is formed on the surface of the liquid film 16 to vaporize
the solvent in the liquid film 16. Concretely, as shown in FIG.
38B, N.sub.2 gas is fed into the chamber 201 at a flow rate of
about 5 L/min, and an air current is formed over the surface of the
liquid film 16.
Moreover, as shown in FIG. 38C, the leveling treatment is performed
while the substrate 11 is in the stationary state (=rotation speed
of 0 rpm). Thereafter, the substrate 11starts to be rotated during
the drying treatment. The rotation speed of the substrate is
rapidly increased in the index function manner until the rotation
speed reaches about 300 rpm. In this case, the rotation speed is
increased in accordance with the film thickness of the liquid film
16. By the centrifugal force, the liquid film 16 is pushed back
onto the peripheral edge, and the solid content can be inhibited
from moving onto the middle portion.
Note that as a result of the monitoring/controlling of the film
thickness of each point, in one example, the flow rate of the air
current and the rotation speed are increased in the index function
manner, but this is not limited. A timing for controlling the
rotation speed of the substrate and starting the rotation can be
changed in accordance with the state of the film thickness. For
example, when the liquid film obtains a predetermined film
thickness, the rotation speed of the substrate may linearly
(=linear function manner) be increased to control the film
thickness.
This drying treatment will be described with reference to FIGS. 39A
to 39C. FIG. 39A is a diagram showing the change of the film
thickness of the liquid film in each position on the substrate with
time in the leveling and drying treatments according to the fifth
embodiment, FIG. 39B is a diagram showing the change of the flow
rate of N.sub.2 gas supplied into the chamber with time in the
leveling and drying treatments according to the fifth embodiment,
and FIG. 39C is a diagram showing the change of rotation speed of
the substrate in the leveling and drying treatments according to
the fifth embodiment. FIGS. 39A to 39C continuously show the states
of the above-described leveling and drying treatments.
As shown in FIG. 39A, after the leveling treatment, the difference
in the film thickness is controlled to be within a given range in
the respective points P.sub.1, P.sub.2, P.sub.3 on the substrate
11, the solvent of the liquid film 16 is vaporized until a
predetermined film thickness (e.g., 400 nm) is obtained, and a
drying treatment is performed.
At this time, after the leveling treatment ends, an inactive gas
(e.g., N.sub.2, Ar) is fed into the chamber 201, and an air current
is supplied onto the surface of the liquid film 16 to vaporize the
solvent. Concretely, as shown in FIG. 39B, N.sub.2 is supplied into
the chamber 201 at about 5 L/min, and an air current is formed over
the surface of the liquid film 16.
Moreover, as shown in FIG. 39C, the leveling treatment is performed
while the substrate 11 is in the stationary state (=rotation speed
of 0 rpm). At the drying treatment time, when the film thickness of
the liquid film 16 reaches the predetermined value, the substrate
11starts to be rotated. In the present embodiment, when the film
thickness of the liquid film 16 reaches 6.0 .mu.m, the substrate 11
starts to be rotated. The rotation speed of the substrate 11 is
linearly (=linear function manner) increased to reach about 300
rpm. The rotation speed of the substrate 11 is increased in
accordance with the film thickness of the liquid film 16. By the
centrifugal force, the liquid film 16 is inhibited from flowing
into the middle portion from the peripheral edge, and the solid
content can be inhibited from moving onto the middle portion.
In the present embodiment, in one example, the drying treatment is
performed until the film thickness of the solid film is
substantially obtained (e.g., 400 nm), and the film thickness of
the liquid film 16 does not change. Concretely, the treatment is
performed until the concentration of the solid content in the
liquid film 16 reaches 80% or more. After the drying treatment, a
baking treatment is performed to vaporize the remaining solvent,
and the film is stabilized. However, the process is not limited to
the above-described process. For example, after ending the drying
treatment in a stage in which the film thickness of the liquid film
still changes, a baking treatment can also be performed. In this
case, the drying treatment ends, when the liquid film 16 reaches
predetermined film thickness (e.g., 1.0 .mu.m). Thereafter, the
baking treatment is performed to stabilize the film, and a solid
film having a film thickness of 400 nm is formed.
Note that, here, to prepare for the supply of the air current to
the liquid film 16, the air current control wall described above
with reference to FIG. 35 can be disposed in the leveling/drying
treatment apparatus 200 shown in FIG. 36.
As described above, in the present embodiment, as needed, the film
thickness in each point is monitored, the leveling and drying
treatments are performed, and the respective treatment parameters
(=concentration and pressure of the solvent in the chamber,
temperature distribution of the substrate, air current required for
the drying treatment, and rotation speed of the substrate) are
controlled until these treatments end, but the present invention is
not limited to this.
For example, as described hereinafter, in the leveling treatment
and in the initial stage of the drying treatment, a control
function is derived by fitting the value of each treatment
parameter with respect to time. Thereafter, the control may also be
executed based on the derived control function until the end of
each treatment.
f(P, t)=0
f(T, t)=0
f(V, t)=0
f(R, t)=0
P:pressure in the chamber
T:temperature of the substrate
V:flow rate of the air current
R:rotation speed of the substrate
t:time
Moreover, as described above, after once deriving the control
function, the control function is stored in the analysis unit 210.
In the treatment of the second and subsequent substrates, without
monitoring the film thickness of the liquid film 16, each treatment
can be performed while referring to the control function of the
analysis unit 210.
For example, to perform the drying treatment by the control of the
rotation speed of the substrate 11, from start time t.sub.A of the
drying treatment till time t.sub.B, the film thickness of the
liquid film 16 in each point is measured and monitored, and the
rotation speed of the substrate 11 is controlled till the initial
stage. FIG. 40A shows tendency of the change of the film thickness
of the liquid film 16 at d=-0.16 t+10 (d:film thickness, t: time).
Moreover, FIG. 40B shows the rotation speed of the substrate in
accordance with the film thickness change shown in FIG. 40A. At
this time, when the change of the rotation speed of the substrate
with respect to the change with time t.sub.A to t.sub.B is derived
as the function by the fitting, the rotation speed of the
substrate: R=2.5 e.sup.0.7t. Therefore, from time t.sub.B until end
time t.sub.C of the drying treatment, the rotation speed of the
substrate 11 is controlled in accordance with the function: R=2.5
e.sup.0.7t.
For the second and subsequent substrates, the rotation speed of the
substrate 11may be controlled in accordance with the control
function: R=2.5 e.sup.0.7t.
Note that the solid content does not move with the movement of the
solution in the transverse direction of the substrate. In this
case, the respective conditions such as the temperature of the
substrate at the drying time, air current of the drying treatment,
atmosphere concentration in the chamber, and pressure are changed
using a test substrate beforehand. Moreover, the film thickness is
measured by reflected light measurement in a plurality of points
including at least the substrate center, coating start position,
and coating end position. From these results, a condition on which
the interference fringes of the reflected light are generated with
respect to the film thickness of the liquid film in one direction,
or toward the outer periphery from the substrate center may be
determined.
As described above, the present embodiment comprises: forming a
liquid film; subsequently continuously performing a leveling and
drying treatments; controlling the film thickness difference of the
liquid film as needed in each treatment step; and forming the film
including the solid content on the substrate. Therefore, when the
film thickness of the liquid film in each point is within the
predetermined range after forming the liquid film on the substrate,
the drying treatment can also be performed without performing the
leveling treatment. Moreover, after the leveling treatment,
depending on the material of the liquid film, the solid content
hardly moves during the drying treatment. In this case, as
described above, the film thickness is not particularly controlled,
the solvent of the liquid film is vaporized in the related-art
method, and the drying treatment can also be performed. In this
case, a magnitude relation of the temperature may be reversed in
the middle portion and peripheral edge of the substrate so as to
perform the drying treatment. That is, in the process in which the
drying treatment is performed, the temperature of the middle
portion of the substrate is set to be lower than that of the
peripheral edge, so that the solvent of the liquid film can also be
vaporized.
Additionally, the constitution of the leveling/drying treatment
apparatus can appropriately be changed without departing from the
scope of the present invention, and the substrate to be actually
coated and solution may be used to carry out the experiment
described in the present embodiment and to determine each
condition.
Sixth Embodiment
FIGS. 41A to 41E are process sectional views showing a
manufacturing process of a semiconductor apparatus according to a
sixth embodiment of the present invention.
First, as shown in FIG. 41A, a liquid film 302 including a resist
solution is formed on a substrate 301. The resist solution is
obtained by dissolving a chemical amplification type resist
material (first material) obtained by blending a resin, dissolution
inhibitor material, and acid generating material at a given ratio
in ethyl lactate (solvent). The resist solution is adjusted so as
to set the film thickness of the resist film (solid film) including
the resist material finally to 300 nm in the state in which the
solvent in the liquid film is completely evaporated. Note that the
substrate 301 includes the semiconductor substrate, and is in the
middle of the manufacturing process of the semiconductor
apparatus.
An outline of the liquid film forming apparatus for use in forming
the liquid film 302 is shown in FIG. 42.
The apparatus shown in FIG. 42 will next be described. As shown in
FIG. 42, a substrate hold portion 330 on which the substrate 301 is
mounted is connected to a driving system 331 which rotates
centering on the substrate 301. Moreover, a solution discharge
nozzle 332 which discharges the solution and which can be moved in
the diameter direction by a nozzle driving system 333 is disposed
above the substrate 301. The solution discharge nozzle 332 is
connected to a solution supply pump 335 which supplies the solution
to the solution discharge nozzle 332 via a solution supply tube
334. The discharge speed from the solution discharge nozzle 332 is
controlled by controlling a solution supply pressure from the
solution supply pump 335.
The solution discharge nozzle 332 starts movement substantially
from the center of the substrate 301 by the nozzle driving system
333, and continuously supplies the solution onto the substrate 301
while substantially moving to the edge of the substrate 301. The
solution supply ends when the solution discharge nozzle reaches the
edge of the substrate 301. In movement start and end points of the
solution discharge nozzle, solution cut-off functions 336a, 336b
are disposed. The solution cut-off function 336a in the movement
start point cuts off the solution discharged from the solution
discharge nozzle 332 until the rotation speed of the substrate hold
portion 330, movement speed of the nozzle driving system 333, and
discharge speed from the solution discharge nozzle 332 reach
predetermined values required at the coating start time, and
prevents the solution from reaching the substrate 301. Moreover,
the solution cut-off function 336b in the movement end point is on
standby above the edge of the substrate 301 so as to prevent the
solution from being supplied to the edge of the substrate 301, and
cuts off the solution discharged from the nozzle 332, when the
solution discharge nozzle 332 reaches the edge of the substrate
301. The solution is thus prevented from reaching the substrate
301.
While the solution is supplied onto the substrate 301, the rotation
speed of the substrate hold portion 330, movement speed of the
nozzle driving system 333, and discharge speed from the solution
discharge nozzle 332 are managed by a rotation driving control unit
338, nozzle driving control unit 337, and solution supply pump 335.
Note that a controller 339 for controlling the pump 335 and control
units 337, 338 is disposed upstream.
The controller 339 determines the rotation speed of the substrate
301, movement speed of the solution discharge nozzle 332, and
discharge speed from the solution discharge nozzle 332 based on
position information of the solution discharge nozzle 332 on the
substrate 301, and instructs the rotation driving control unit 338,
nozzle driving control unit 337, and solution supply pump 335. When
these operated based on the instruction, the solution is supplied
in a spiral form onto the substrate 301. The solution supplied onto
the substrate 301 spreads, and is combined with the adjacent liquid
film to form one liquid film 302 on the substrate 301.
For the resist solution for use in the above-described two
apparatuses, a solution having a small solid content, and low
viscosity in a range of about 0.001 Pas to 0.010 Pas (1 cp to 10
cp) is used.
The discharging of the solution onto the substrate 301 from the
solution discharge nozzles 322, 332 by the above-described
apparatus will be described with reference to FIG. 43. FIG. 43 is a
sectional view for use in the description of the discharge state of
the solution by the liquid film forming apparatus shown in FIG. 42.
As shown in FIG. 43, the solution discharge nozzles 322, 332
spirally discharge solutions 342a, 342b, 342c in adjacent
positions. The spirally discharged solutions 342a, 342b, 342c
spread by the fluidity of the solutions with time to form one
liquid film. Moreover, as shown in FIG. 41A, the surface of the
connected liquid film has a substantially flat shape by the surface
tension of the liquid.
Subsequently, the solvent in the liquid film 302 is removed. To
remove the solution, the substrate having the liquid film formed on
the main surface thereof is exposed under a reduced pressure, or
heated using an oven or hot plate, the solvent in the liquid film
is evaporated, and the solvent can be removed.
When the removal of the solvent proceeds to some degree, as shown
in FIG. 41B, a first resist layer 311 of the lower layer including
the resist material is formed from a direction of a lower part of
the liquid film 302. Moreover, in the surface layer of a liquid
film 302a in which the solvent is being evaporated, the viscosity
is in a high state.
To remove the solvent, the film thickness of the first resist layer
311 being formed is measured. The film thickness of the first
resist layer 311 can be obtained, for example, by irradiating the
liquid film 302 with a light from the light source having a single
wavelength as a collimated light, monitoring a reflected light
intensity, capturing an interference waveform in the liquid film,
and analyzing the waveform using an optical constant (refractive
index and attenuation coefficient) of the liquid film.
When the film thickness of the first resist layer 311 being formed
reaches 290 nm, the removing of the solvent once stops.
Subsequently, as shown in FIG. 41C, the removal of the solvent is
once stopped, a second solution (second material solution) 303 in
which the dissolution inhibitor material included in the
above-described resist material is dissolved in ethyl lactate is
sprayed onto the surface of the liquid film 302 in the process of
solidifying, and the dissolution inhibitor material is supplied to
the surface of the liquid film 302a. To spray the second solution
303, for example, the substrate 301 including the liquid film 302a
remaining on the surface thereof is laid in a container filled with
a mist solution.
Moreover, to spray the second solution 303, the substrate 301 is
rotated, and the solution can be supplied in a mist form
substantially from above the rotation center of the substrate 301.
When the substrate 301 is rotated, the air current directed toward
the outside of the substrate substantially from the rotation center
is generated. When the mist solution is supplied substantially from
above the rotation center, the mist solution rides on the air
current, and the solution is substantially uniformly sprayed over
the whole surface of the substrate 301.
Thereafter, the solvent (ethyl lactate) is continuously removed,
the solvent in the liquid film is completely removed, and a solid
resist film (solid film) 310 is formed as shown in FIG. 41D. The
resist film 310 is constituted of the first resist layer 311 and
second resist layer 312 on the first resist layer 311. The second
resist layer 312 has a film thickness of 10 nm. As a result of
material analysis such as XPS, it has been confirmed that much
dissolution inhibitor is distributed in the second resist layer 312
as compared with the first resist layer 311.
According to the above-described method, the dissolution inhibitor
material is added to the surface of the liquid film 302a during the
drying, the solvent is further removed, and it is possible to
easily form the resist film 310 which has a different composition
only in the surface layer. Since it is unnecessary to separately
form the resist film having the different composition, a
manufacturing time of the resist film different in the composition
in the film thickness direction is shortened.
Subsequently, as shown in FIG. 41E, after exposure and
post-exposure bake treatment (PEB) are performed, development is
performed to form a resist pattern 313.
As shown in FIG. 41E, the upper part of the first resist layer 311
is rounded, but the upper surface of the second resist layer 312 is
maintained in a rectangular shape.
The exposure, post-exposure bake treatment, and development of the
chemical amplification type resist film will briefly be described.
When the acid generating material in the chemical amplification
type resist film is irradiated with light, the acid generating
material is decomposed and acid molecules are generated. Moreover,
the resist film is heated, then the acid molecules decompose the
dissolution inhibitor material, and the dissolution inhibitor
material is changed into a molecular structure which can be
dissolved in a developer.
The shape of the resist pattern prepared from the resist film
formed in the related-art method is shown in FIG. 44. A resist
pattern 351 shown in FIG. 44 is prepared on the same conditions as
those of the exposure and development of the resist pattern 313
shown in FIG. 41E.
The reason why the shape of the upper surface of the second resist
layer 312 is maintained in the rectangular shape will be described
hereinafter. The upper surface of the resist film is exposed to the
developer for a long time. Therefore, with the resist film in which
the dissolution inhibitor material is uniformly distributed, the
upper part is rounded. However, when much dissolution inhibitor is
included in the surface as in the present embodiment, the
development speed in the upper part can be lowered, and the surface
shape can be rectangular.
As described above, when the present method is used, the profile of
the resist pattern can easily be improved.
Note that in the method described in the present embodiment, the
evaporation is not performed at all, the second solution is
supplied onto the liquid film in this state, and the dissolution
inhibitor material in the second solution is diffused in the liquid
film. Therefore, in the state in which the solvent is removed to
some degree and the resist film is formed in the lower part, the
second solution has to be supplied onto the liquid film.
Note that in the present embodiment the second resist layer 312
including much dissolution inhibitor is formed in a range of 10 nm
from the surface, but this is not limited. This differs by the
exposure, post-exposure bake, and development conditions.
Therefore, in order to obtain the desired resist pattern,
experiments are repeatedly conducted, and the film thickness width
including much dissolution inhibitor and the amount of the
dissolution inhibitor may be optimized. Moreover, the resist film
described in the present embodiment is defined as a photo-sensitive
resin film which contains photosensitive polyimide.
The film thickness of the layer including much dissolution
inhibitor is determined by the timing to supply the second
solution. That is, the thickness is determined by the amount of the
liquid film formed on the solid film being formed. Therefore, in
the method described in the present embodiment, it is important to
grasp the evaporation state of the solvent.
For the resist solution for use in the above-described two
apparatuses, the solution containing a large amount of solvent in
the liquid film is used. Therefore, much time is required for
removing the solvent, and it is easy to grasp the evaporation state
of the solvent. Therefore, in the method described in the present
embodiment, the above-described liquid film forming apparatus is
preferably used.
Note that the method described in the present embodiment can also
be applied to the liquid film formed by a spin coating method.
Moreover, the present invention can also be applied to the liquid
film prepared in various methods such as a method of discharging or
spraying the solution to form the film, and a method of using the
meniscus phenomenon to form the film, as disclosed in Jpn. Pat.
Appln. KOKAI Publication Nos. 2-220428, 6-151295, 7-321001,
2001-310155, and 11-243043.
Moreover, in the present embodiment, the same dissolution inhibitor
material as that contained in the resist material is used as the
dissolution inhibitor material, but this is not limited. As long as
the desired resist pattern profile is obtained, any available
material may also be used. Also in this case, the experiments are
repeatedly conducted, the material is selected, and the film
thickness width to be added and addition amount may be
optimized.
Moreover, in the present embodiment, the removal of the solvent is
once stopped, the solution in which the dissolution inhibitor
material included in the above-described resist is dissolved in
ethyl lactate is sprayed onto the liquid film surface in the
process of solidification, and thereafter the solvent (ethyl
lactate) is continuously removed, but this is not limited.
For example, while the solvent is removed, the spray amount of the
solution containing the dissolution inhibitor material dissolved in
the ethyl lactate is increased with time to form the resist film,
and it is also possible to raise the concentration of the
dissolution inhibitor material in the vicinity of the film
surface.
When the resist film is subjected to this treatment, as shown in
FIG. 45, a rectangular satisfactory resist pattern 361 can be
obtained. In FIG. 45, a second resist layer 312' has a dissolution
inhibitor material concentration higher than that of the first
resist layer 311, and is a resist film which has a profile having
the high dissolution inhibitor material concentration in the
vicinity of the surface. FIG. 45 is a sectional view showing the
shape of the resist pattern prepared using the resist film having
the profile which has the higher dissolution inhibitor material
concentration closer to the surface.
Moreover, in the present embodiment, the layer including more
dissolution inhibitor in the resist film surface is formed in
consideration of pattern deterioration during the development, but
this is not limited.
For the film in which evaporation of acid at a bake or exposure
time as a problem in the chemical amplification type resist is
remarkably seen, in consideration of the amount of acid lost at the
bake and exposure time, the acid generating material is selected as
the second material, and the resist film containing more acid
generating materials may be formed in the resist film surface in a
method similar to that of the present embodiment. Also with respect
to the acid generating material for use herein, the experiments are
repeatedly conducted for the film thickness width to be added and
addition amount with respect to the available material, the
material is selected, and the film thickness width to be added and
addition amount may be optimized.
The evaporation of acid occurs particularly remarkably in the film
surface. Therefore, the spray amount of the solution obtained by
dissolving the acid generating material in the solvent is
preferably increased with time.
Of course, to establish both a countermeasure against the
evaporation of acid at the bake or exposure time and a
countermeasure against the pattern deterioration at the development
time, the dissolution inhibitor material and acid generating
material are selected as the second materials. The resist film
which contains more dissolution inhibitor and acid generating
materials in the resist film surface may also be formed in a method
similar to that of the present embodiment. Also with respect to the
acid generating material for use herein, the experiments are
repeatedly conducted for the film thickness width to be added and
addition amount with respect to the available material, the
material is selected, and the film thickness width to be added and
addition amount may be optimized. Also in this case, the spray
amount of the solution obtained by dissolving the acid generating
material and dissolution inhibitor material in the solvent is
preferably increased with time.
Examples of the resist as the object to which the present technique
is applied include: chemical amplification type resists which have
photo sensitivity with respect to deep-UV and vacuum ultraviolet
light, such as KrF, ArF, and F.sub.2 lasers (energy line); chemical
amplification type resists which have photo sensitivity to high and
low-acceleration electron beams (energy lines); and chemical
amplification type resists which have photo sensitivity to ion
beams (energy lines).
Note that the second material is scattered without being dissolved
in the solvent, the solvent remains in the surface layer in the
liquid film, and the second material may be supplied to the liquid
film in this state.
Moreover, when a goal of changing the composition of a film
thickness direction can be achieved using the same composition for
the first and second materials, the same composition may be used in
the first and second materials.
Seventh Embodiment
It is proposed to use an SiOC composition film whose permittivity
is lower than that of an SiO.sub.2 film as the interlayer
insulating film for use in the semiconductor apparatus. Since the
SiOC composition film is not dense, the material of a wiring formed
in the surface is easily diffused. Therefore, the dense film such
as the SiO.sub.2 film is formed on the surface of the SiOC
composition film in order to prevent the material from being
diffused.
The SiOC composition film and SiO.sub.2 film have to be thus
separately formed, and the number of steps has increased. In the
present embodiment, a manufacturing method of the semiconductor
apparatus will be described in which the SiOC composition film and
SiO.sub.2 film are continuously formed so as to reduce the number
of steps.
FIGS. 46A to 46C are process sectional views showing the
manufacturing process of the semiconductor apparatus according to a
seventh embodiment.
First, as shown in FIG. 46A, on a substrate 401, a liquid film 402
is formed including a solution (solid content of 10%) in which the
first material mixed at a ratio of SiO.sub.2:SiOCH.sub.3=1:r.sub.1
is dissolved in the solvent. The liquid film 402 is formed in a
method similar to the forming method described in the first
embodiment. Note that the substrate 401 includes the semiconductor
substrate and is in the middle of the manufacturing process of the
semiconductor apparatus.
Subsequently, the substrate 401 on which the liquid film 402 is
formed is contained in the pressure reduction chamber. The liquid
film is exposed to the reduced pressure substantially equal to the
vapor pressure of the solvent included in the liquid film 402, and
the solvent in the liquid film is slowly removed. The liquid film
surface is vertically irradiated with a monochromatic light of 470
nm, the reflected light intensity change is monitored, and the
removal process of the solvent is detected.
At a forming time of the liquid film 402, the thickness was about
10 .mu.m (solid content of 10%). As shown in FIG. 46B, in a stage
in which the height of the surface of a liquid film 402a from the
surface of the substrate 401 is 1.5 .mu.m, a second solution
(second material solution) 403 in which a second material mixed at
a ratio of SiO.sub.2:SiOCH.sub.3=1:r.sub.2 (r.sub.1>r.sub.2) is
dissolved in the solvent starts to be introduced into the pressure
reduction chamber. A numeral number 411 denotes an SiOC composition
film.
The second solution 403 is supplied in a state in which the
pressure in the pressure reduction chamber is maintained. It has
been confirmed that the second solution 403 is sprayed as mist onto
the liquid film 402a surface in the pressure reduction chamber. The
ratio r.sub.2 is gradually reduced toward 0 with respect to a
supply start time of the second solution 403, the supply amount of
SiOCH.sub.3 is changed. Moreover, in a stage in which the ratio
r.sub.2 turns to 0, the pressure in the pressure reduction chamber
is lowered, and the second solution 403 containing only SiO.sub.2
is introduced into the pressure reduction chamber. After an elapse
of 30 seconds, the introduction of the second solution 403 is
stopped.
The reduced pressure state is held for one minute after the
introduction is stopped. The solvent is removed, and as shown in
FIG. 46C, an SiOC composition film (solid film) 410 is formed.
After the SiOC composition film 410 is formed, the pressure
reduction chamber is opened, and the substrate 401 is removed. The
thickness of the finally formed SiOC composition film 410 was 1.2
.mu.m.
A distribution of the film thickness direction of oxygen and carbon
with respect to Si in the obtained SiOC composition film 410 was
obtained by analysis, and the result is shown in FIG. 47. As shown
in FIG. 47, it is seen that a layer having a uniform composition of
O/Si=1.8, C/Si=0.2 is obtained in the lower-layer film 411 in 0.8
.mu.m from a bottom surface. It has been confirmed that a ratio of
O gradually increases and ratio of C gradually decreases in an
intermediate-layer film 412 between 0.8 .mu.m and 1.1 .mu.m.
Furthermore, for an upper-layer film 413 having a film thickness of
0.1 .mu.m on the intermediate-layer film 412, the existence of C is
not seen, and it has been confirmed that the film having an
SiO.sub.2 composition is formed.
As described above, in a pressure reduction solvent removal
process, the solution in which SiO.sub.2 is dissolved is supplied
to the liquid film being solidified, and thereby the
low-permittivity interlayer insulating layers (0 to 1.1 .mu.m) 411,
412 and upper-layer film (1.1 to 1.2 .mu.m) 413 can easily be
obtained.
Here, since the film to be finally formed is the SiO.sub.2 film,
the solution with only SiO.sub.2 dissolved therein may be supplied
to the liquid film. However, as described above, the supply amount
of SiOCH.sub.3 is gradually reduced, and finally only SiO.sub.2 is
supplied to the liquid film. The reason why the supply amount of
SiOCH.sub.3 is gradually reduced will be described hereinafter.
SiO.sub.2 is hydrophilic, and SiOCH.sub.3 has properties between
hydrophilic and hydrophobic properties. For the liquid film,
SiO.sub.2 and SiOCH.sub.3 are dissolved in the solvent. When the
solution with only SiO.sub.2 dissolved therein is supplied in the
mist form onto the liquid film in this state, the properties of the
liquid film and solution differ from each other, and the solution
with SiO.sub.2 dissolved therein is condensed. Then, in order to
inhibit the solution containing SiO.sub.2 from being condensed, the
supply amount of SiOCH.sub.3 is gradually reduced, and the property
of the solution is gradually changed.
Note that even with the supply of the second solution onto the
liquid film, the material included in the second solution is not
condensed, and in this case it is unnecessary to gradually change
the mixture ratio.
Note that the film having a different composition ratio in the film
thickness direction can be formed even using materials other than
the above-described materials. The material whose composition ratio
is known can be applied to the formation of the film constituted of
any material.
Note that the supply timing of the second solution may be adjusted
so as to obtain the desired permittivity. To determine the actual
supply timing and the materials included in the liquid film and
second solution, the composition ratio of the materials included in
the liquid film, concentration of the solid content in the liquid
film, pressure reduction condition, composition ratio of the
materials included in the second solution, solid content
concentration in the second solution, supply speed into the
chamber, and supply time are used as parameters to form a plurality
of films. Subsequently, with respect to the formed films, the
composition of the film thickness direction is analyzed by element
analysis, the permittivity is measured, and the parameters may be
determined so as to obtain the predetermined film conditions.
Moreover, the above-described method is not limited to the
formation of the SiOC composition film, and can also be applied to
the forming of an electrode or wiring. In this case, an electrode
or wiring material may be used in the first material, and a
diffusion inhibitor material may be used in the second material for
the purpose of preventing the first material from being diffused.
To determine the materials or supply timing of the second material,
in the same manner as in the above-described interlayer film
formation, the composition ratio of the first materials,
concentration of the materials dissolved in the solvent, solvent,
pressure reduction condition, composition ratio of the second
materials, concentration of the materials dissolved in the solvent,
solvent, supply speed into the chamber, and supply time are used as
the parameters to form the films. Subsequently, with respect to the
formed films, the composition of the film thickness direction is
analyzed by element analysis, the permittivity is measured,
resistance value is also measured, and the respective parameters
may be determined so as to obtain the desired film conditions.
Eighth Embodiment
The present invention relates to a method of using a coating type
silica glass film to form a film which has a distribution of photo
acid generating materials on the surface.
As described as the problem in Jpn. Pat. No. 2842909, when the
conventional silica glass film is used, acid generated by the
chemical amplification type resist at the exposure time is diffused
in the silica glass film, and problems such as an opening defect
are caused.
In Jpn. Pat. No. 2842909, it is described that an acid material is
introduced into the surface of the silica glass film, and thereby
opening defects can be prevented.
In an eighth embodiment, a method of using the above-described
method to manufacture the silica glass film (silica dioxide
compound) which contains the acid material in the surface will be
described.
FIGS. 48A to 48E are sectional views showing the manufacturing
processes of the semiconductor apparatus according to the eighth
embodiment of the present invention.
First, as shown in FIG. 48A, on a substrate 501, a liquid film 502
is formed including a first solution in which the first material
mixed at a ratio of SiO.sub.2:SiOCH.sub.3=1:a.sub.1 is dissolved in
the solvent. For the forming method of the liquid film, a method
similar to that described in the first embodiment is preferably
used. The solid content in the liquid film 502 is 3%, and the
thickness at the liquid film forming time is about 10 .mu.m. Note
that the substrate 501 includes the semiconductor substrate and is
in the middle of the manufacturing process of the semiconductor
apparatus.
Subsequently, the substrate 501 on which the liquid film 502 is
formed is inserted into the pressure reduction chamber. The liquid
film is exposed to the reduced pressure substantially equal to the
vapor pressure of the solvent included in the liquid film 502, and
the solvent in the liquid film 502 is slowly removed. The surface
of the liquid film 502 is vertically irradiated with monochromatic
light of 470 nm, and the removing process of the solvent is
monitored from the reflected light intensity change.
As shown in FIG. 48B, in a stage in which the height of the surface
of a liquid film 502a is 0.4 .mu.m, the pressure in the pressure
reduction chamber is maintained, and a second solution 503 in which
photo acid generating materials such as sulfonate are dissolved in
the solvent starts to be introduced into the pressure reduction
chamber. It has been confirmed that the second solution 503 is
sprayed as mist onto the liquid film 502a surface in the pressure
reduction chamber. After the elapse of 30 seconds, the pressure
reduction chamber is opened and the substrate is removed. Note that
a numeral number 511 denotes a lower-layer film from which the
solvent is removed and which includes SiO.sub.2 and
SiOCH.sub.3.
As shown in FIG. 48C, the thickness of a silica glass film 510
formed by removing the solvent was 0.3 .mu.m. As a result of
physicochemical analysis, it has been confirmed that the acid
generating material is included in an upper-layer film 512 in a
range of 20 nm from the film surface.
Subsequently, as shown in FIG. 48D, a chemical amplification type
resist film 520 is formed on the silica glass film 510. The
chemical amplification type resist film 520 is successively
subjected to pre-exposure baking and cooling. Thereafter, with
respect to the chemical amplification type resist film 520, the
predetermined pattern is exposed. After exposure, post-exposure
baking and cooling are performed.
Subsequently, as shown in FIG. 48E, the chemical amplification type
resist film 520 is developed to form a resist pattern 521.
For the silica glass film 510 prepared according to the present
embodiment, since the photo acid generating material is distributed
in the upper-layer film 512 of the surface, the above-described
problem can be solved. Even when the film is coated with the
chemical amplification type resist, exposed, and developed to
prepare the device pattern, a resist process superior in
dimensional uniformity can be performed without any opening
defect.
The present invention is superior to Jpn. Pat. No. 2842909 in that
the acid generation amount of silica glass as a foundation can
easily be adjusted for each chemical amplification type resist
film. This can solve problems that depending on the chemical
amplification type resist film, a slight opening defect has
heretofore been generated because of acid shortage with the use of
silica glass with the same photo acid generating material
introduced therein, and a pattern lower part becomes thin and falls
because of excess acid.
Note that the actually prepared film is coated with the chemical
amplification type and exposed/developed to form the pattern, the
shape and dimension of the pattern are measured, defects are
checked, and thereby the thickness and amount of a region including
the photo acid generating material in the present embodiment may be
optimized.
Ninth Embodiment
A solid film forming method according to the present embodiment
will be described with reference to the process sectional views of
FIGS. 49A to 49C. FIGS. 49A to 49C are the process sectional views
showing the manufacturing processes of the semiconductor apparatus
according to a ninth embodiment of the present invention.
First, as shown in FIG. 49A, a liquid film 602 including the resist
solution is formed on a substrate 601 which includes a 1 .mu.m
stepped portion and whose area ratio of a convex portion to a
concave portion is 1:1. At the forming time of the liquid film 602,
the liquid film is formed so that a thickness h of the liquid film
602 is larger than 10.5 .mu.m. In the present embodiment, the
liquid film 602 was formed so as to set an average height to 15
.mu.m.
The liquid film 602 is formed using the liquid film forming
apparatus described in the sixth embodiment and shown in FIG. 42.
As a concrete condition, on the substrate fixed onto the stage, the
solution discharge nozzle (.phi.40 .mu.m) is reciprocated/moved by
the nozzle driving unit in the column-direction at a speed of 1
m/s. When the solution discharge nozzle is positioned outside the
substrate, the stage is successively moved by the stage driving
unit at a pitch of 0.3 mm in the row-direction, and the resist
solution (solid content of 3.0%) is linearly discharged to form the
liquid film 602.
Note that to adjust the thickness of the liquid film 602, any one
of the solid content in the solution, relative movement pitch of
the substrate and solution discharge nozzle, relative movement
speed, and discharge amount of the solution is controlled.
Subsequently, as shown in FIG. 49B, the substrate 601 on whose
surface the liquid film 602 is formed is sealed in the treatment
container filled with the atmosphere of the solvent for 60 seconds,
and the liquid film 602 surface is leveled (flatted).
Next, as shown in FIG. 49C, the solvent in the liquid film 602 is
removed, and a resist film 603 including the solid content in the
liquid film 602 is formed. One example of the removal of the
solvent in the liquid film 602 will be described hereinafter. The
substrate is contained in a pressure reduction drying treatment
unit including an infrared irradiation portion shown in FIG. 50,
and the treatment container is exhausted at a pressure reduction
speed of -100 Torr/sec. When the pressure in a treatment container
611 reaches 2 Torr as the vapor pressure of the solvent in the
liquid film, the liquid film 602 on the substrate 601 is irradiated
with infrared rays from an infrared irradiation portion 612. Note
that an infrared wavelength is set to a range of 2.5 to 3.0 .mu.m
including a wavelength to be absorbed by the solvent of a coat
liquid for use. The whole substrate surface is irradiated with the
infrared rays through a quartz window 613 from the outside of the
treatment container 611. By the pressure reduction effect and the
heating by the infrared rays, the solvent in the liquid film 602 is
rapidly vaporized, and the resist film 603 constituted of the solid
content included in the solution is formed on the substrate 601 in
two seconds.
The film thickness distribution of the coat film which is formed by
the above-described process and which includes a 1.0 .mu.m stepped
portion on the substrate is shown in FIG. 51A. As shown in FIG.
51A, the thickness of the resist film 603 formed in the concave
portion of the substrate 601 was 0.465 .mu.m and the thickness of
the resist film 603 formed in the convex portion was 0.435 .mu.m. A
difference in the thickness between the coat films formed on the
concave and convex portions is about 7% with respect to an average
film thickness of 0.450 .mu.m and the coat film can thus be formed
along the substrate surface with good uniformity.
Two samples including liquid films having different film
thicknesses were formed in a method different from the
above-described film forming method, and were compared with the
resist film formed in the method described in the present
embodiment. Additionally, the solid content in the solution was
changed so that the average value of the film thicknesses of the
resist films in the concave and convex portions formed in two
samples was 0.450 .mu.m, in the same manner as in the resist film
formed in the above-described method.
Sample B: formed using a resist solution including a solid content
of 6.4% so that the average height of the liquid film is 7
.mu.m.
Sample C: formed using the liquid film of the resist solution
including a solid content of 9% so that the average height of the
liquid film is 5 .mu.m.
The film thickness distributions of the coat films in the
respective samples B, C are shown in FIGS. 51B, 51C. With the
sample B, the film thickness of the concave portion of a resist
film 603' was 0.48 .mu.m, and the film thickness of the convex
portion of the resist film 603' was 0.416 .mu.m. The film thickness
difference with respect to the average film thickness of 0.45 .mu.m
deteriorated at about 14%. With the sample C, the film thickness of
the concave portion of a resist film 603'' was 0.495 .mu.m, and the
film thickness of the convex portion of the resist film 603'' was
0.405 .mu.m. The film thickness difference with respect to the
average film thickness of 0.45 .mu.m greatly deteriorated at about
20%.
The above-described results are shown in a graph of FIG. 52. As
shown in FIG. 52 and as described above, the coat film can
uniformly (film thickness difference within 10%) be formed along
the concave/convex portion on the concave/convex substrate only
with the sample using the present method. Note that FIG. 52 shows
the sample formed in the method described in the present embodiment
as the sample A.
The effect of the present invention will next be described.
By the above-described coating method, the liquid film is formed on
the substrate including the stepped portion at a ratio of the
concave portion to the convex portion, which is 1:1. Thereafter,
the liquid film flows into the concave portion from the convex
portion by the fluidity of the liquid film and is smoothed.
Therefore, after the leveling step, there is no stepped portion in
the concave/convex portion in the liquid film surface (FIG. 49B).
Therefore, when the solvent is rapidly vaporized from the liquid
film in this state, each solid film thickness formed in the
concave/convex portion in a unit area of the solid content is
represented by the following equations (12), (13):
.times..times..times..times..times. ##EQU00001##
h: average liquid film thickness
d: stepped portion height
p: solid content (ratio)
c.sub.S: density of the liquid film
c.sub.L: density of the solid content in the solid film
A condition on which the difference of the film thicknesses of the
concave and convex portions is 10% is represented by equation
(14):
.times..times..times..times. ##EQU00002##
Therefore, in order to set the difference of the film thickness of
the concave/convex portion to be within 10%, the condition of
equation (15) obtained by solving the equation (14) needs to be
satisfied. h>10.5 d (15)
As shown in the equation (15), the average liquid film thickness
needs to be larger than 10.5 times the stepped portion height.
In the above-described method, since the relation is satisfied, the
film thickness difference can be set to be within the predetermined
range, and the film having a substantially uniform film thickness
along the stepped portion can be obtained. Moreover, the parameters
described in the equation (15) include only shelf height and liquid
thickness, and the solid content and density in the liquid film are
not used.
The concave/convex portion will be described in which a ratio of
the area of the convex portion to the whole area is a
(1>a>0), and a ratio of the area of the concave portion to
the whole area is 1-a. In the leveled state, a film thickness
h.sub.1 in the concave portion and film thickness h.sub.u in the
convex portion are as follows: h.sub.1=h+ad h.sub.u=h+(a-1)d
Therefore, when the solvent is rapidly vaporized from the liquid
film in the leveled state, each solid film thickness formed in the
concave/convex portion in the unit area of the solid content is
represented by the following equations (16), (17):
.times..times..times. ##EQU00003##
The condition on which the difference of the film thicknesses of
the concave and convex portions is 10% is represented by equation
(18):
.times..times..times. ##EQU00004##
Therefore, in order to set the difference of the film thickness of
the concave/convex portion to be within 10%, the condition of
equation (19) obtained by solving the equation (18) needs to be
satisfied: h>(11-a)d (19)
As represented by the equation (19), with the concave/convex
substrate whose ratio of the concave portion is a, the thickness
needs to be larger than (11-a) times the stepped portion height
d.
On the other hand, the resist including the solid content of 1.8%
is used, and the average thickness of the concave and convex
portions of the liquid film is set to 25 .mu.m so that the film
thickness of the solid content after the drying of the solvent is
0.450 .mu.m. In this case, since the relation of the equation (15)
is satisfied, the film thickness of the concave portion is 0.459
.mu.m, that of the convex portion is 0.441 .mu.m, the film
thickness difference is 4%, and the film is thus formed with high
precision as compared with the present invention.
However, as shown in FIG. 53, as seen from the film thickness
distribution over the whole surface of a substrate 601, it has been
confirmed that the film thickness of a resist film 623 largely
fluctuates in substrate peripheral edge regions in the coating
start and end portions, and the film thickness uniformity is
largely deteriorated. This film thickness fluctuation was not seen
when the film was formed with an average liquid film thickness of
15 .mu.m as described above.
As disclosed in Jpn. Pat. KOKAI Publication No. 2001-168021 by the
present inventors, the reason why the film thickness fluctuation is
caused is that the flow by gravity is caused with a liquid
thickness not less than the thickness which can be supported by the
substrate. FIG. 54 shows dependence of fluidity in edge portions on
the liquid film thickness. It is seen that the fluidity rapidly
increases with the thickness exceeding 20 .mu.m. FIG. 55 shows the
dependence of the film thickness uniformity of the convex portion
in the whole substrate surface on the liquid film thickness. The
drawings also show the film prepared with a liquid thickness of 22
.mu.m. It is seen from FIGS. 54, 55 that the film thickness
uniformity is correlated with fluidity and the film thickness
uniformity rapidly deteriorated at a boundary of 20 .mu.m. As
described above, also in the present invention method, in order to
obtain the uniform coat film over the whole concave/convex
substrate surface, it is preferable to satisfy the equation (19)
and to set the liquid film thickness to be less than 20 .mu.m.
As described above, for the film forming method described in the
present embodiments, various conditions can be changed. The liquid
film forming method is not limited to the above-described coating
or spiral coating method. Moreover, the present method can also be
applied to the liquid film prepared in various methods such as a
method of discharging or spraying the solution to form the film,
and a method of using the meniscus phenomenon to form the film as
disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 2-220428,
6-151295, 7-321001, 2001-310155, and 11-243043.
Moreover, the drying method is not limited to the present invention
method. For example, a baking method of heating/drying the
substrate directly with a hot plate, air-current drying method, and
the like may also be used. Additionally, the conditions can be
changed as long as the conditions do not run counter to the scope
of the present invention.
Note that the present invention is not limited to the
above-described embodiments, and can variously modified and carried
out without departing from the scope.
Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *